Key Concept: Relative Humidity, Evaporation, Industrial Applications

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that maintaining a relative humidity of 20\% in a food processing unit prevents microbial growth on food products. This is true because most microbial growth requires higher moisture levels, typically above 60\% relative humidity. The reason given is that low humidity conditions accelerate evaporation and inhibit moisture-dependent microbial activity. This is also true and directly explains the assertion since rapid evaporation removes surface moisture from food, creating an unfavorable environment for microbes. Therefore, both the assertion and reason are correct, and the reason correctly explains the assertion.

Key Concept: Humidity and Evaporation

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
Relative humidity measures how much water vapor is in the air compared to the maximum it can hold at that temperature. When humidity is high ($84\%$ in Kochi), the air is nearly saturated with water vapor, so evaporation slows down as there is little “room” left for more vapor. Conversely, lower humidity ($52\%$ in Delhi) allows faster evaporation because the air can absorb more moisture. Thus, the Assertion is true. The Reason correctly explains why higher humidity reduces evaporation rates by stating that the air is saturated, making it the correct explanation for the Assertion.

Key Concept: Humidity, Sweating, Cooling Effect

a) City A because high humidity prevents sweat from evaporating.
[Solution Description]
High humidity slows sweat evaporation, reducing the cooling effect. So, people will sweat more and feel hotter in City A (85\% humidity) compared to City B (35\% humidity).

Key Concept: Relative Humidity and Evaporation

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that wet clothes dry faster in Delhi compared to Kochi when Delhi has lower humidity ($52\%$) than Kochi ($84\%$). This is true because higher humidity means the air already contains more water vapor, reducing the rate of evaporation. Thus, wet clothes dry slower in high-humidity regions like Kochi compared to low-humidity regions like Delhi. The reason correctly explains the assertion as it links humidity with evaporation rate.

Key Concept: Humidity Measurement

c) Hygrometer
[Solution Description]
A hygrometer is the instrument used to measure humidity, as mentioned in the syllabus.

Key Concept: Relative Humidity

b) Air completely saturated with water vapor
[Solution Description]
According to the syllabus, air saturated with water vapor has a humidity of $100\%$.

Key Concept: Hygrometer, Industrial Applications

c) Hygrometer; 20-40\% relative humidity.
[Solution Description]
A hygrometer measures humidity. Dry storage conditions typically require low humidity (20-40\%). High humidity (60-80\%) promotes microbial growth and spoilage.

Key Concept: Relative Humidity Application

b) Jodhpur, because it has lower humidity
[Solution Description]
Wet clothes dry faster in places with lower relative humidity because the air has more capacity to absorb moisture. Jodhpur has a lower relative humidity ($35\%$) compared to Chennai ($75\%$). Therefore, wet clothes will dry faster in Jodhpur.

Key Concept: Humidity Impact

c) Mumbai with $82\%$ humidity
[Solution Description]
Higher relative humidity means the air is closer to being saturated with water vapor, reducing the evaporation of sweat from the skin. Thus, people are likely to sweat more in cities with higher relative humidity.

Key Concept: Relative Humidity, Evaporation

c) Clothes will dry faster in the desert city due to lower humidity.
[Solution Description]
Higher relative humidity means the air already contains more water vapor, slowing down evaporation. The desert city has lower humidity (25\%), so evaporation will be faster there compared to the coastal city (78\%). Wet clothes will dry faster where humidity is lower.

Key Concept: Humidity Range

c) $60\%-80\%$
[Solution Description]
The syllabus states that humid weather usually falls between $60\%$ and $80\%$ relative humidity.

Key Concept: Hygrometer Usage

d) Hygrometer
[Solution Description]
A hygrometer is the instrument specifically designed to measure humidity. Other instruments measure different weather elements: barometer measures atmospheric pressure, thermometer measures temperature, and anemometer measures wind speed.

Key Concept: Maximum and minimum thermometers, Temperature range, Mean daily temperature

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
To verify the assertion, let’s recall the definition of mean daily temperature. According to the syllabus, it is calculated as:
$\text{Mean daily temperature} = \frac{\text{Maximum temperature} + \text{Minimum temperature}}{2}$.
This formula indeed computes the arithmetic mean (or midpoint) of the maximum and minimum temperatures. For example, if the maximum temperature is 30°C and the minimum is 15°C, the mean daily temperature is $\frac{30 + 15}{2} = 22.5°C$, which is the midpoint between 15°C and 30°C.
Therefore, both the Assertion and Reason are true, and the Reason correctly explains the Assertion.

Key Concept: Mean Daily Temperature, Temperature Statistics

c) 30°C
[Solution Description]
Given:
$\text{Mean daily temperature} = \frac{\text{Max temp} + \text{Min temp}}{2}$
$22 = \frac{\text{Max temp} + 14}{2}$
Multiply both sides by 2:
$44 = \text{Max temp} + 14$
Subtract 14 from both sides:
$\text{Max temp} = 30°C$.

Key Concept: Digital vs Liquid Thermometers

d) They provide more precise and quick readings.
[Solution Description]
Digital thermometers are more precise and can record more data compared to traditional liquid-filled thermometers. They do not rely on the expansion of a liquid and provide faster and more accurate readings. Additionally, digital thermometers can store multiple temperature readings and display them digitally.

Key Concept: Temperature Range Calculation

c) 12°C
[Solution Description]
The range of temperature is calculated as:
$\text{Range} = \text{Maximum temperature} – \text{Minimum temperature}$
Substituting the given values:
$\text{Range} = 31 – 19 = 12^{\circ}C$
Thus, the temperature range is $12^{\circ}C$.

Key Concept: Mean Daily Temperature Calculation

b) $23^\circ C$
[Solution Description]
The mean daily temperature is calculated using the formula: $\text{Mean daily temperature} = \frac{\text{Maximum temperature} + \text{Minimum temperature}}{2}$. Substituting the given values: $\frac{30 + 16}{2} = \frac{46}{2} = 23^\circ C$.

Key Concept: Range of Temperature, Mean Daily Temperature

c) 11°C
[Solution Description]
First, calculate the mean daily temperature for Day 1:
$\text{Mean daily temperature} = \frac{\text{Maximum temperature} + \text{Minimum temperature}}{2} = \frac{32 + 18}{2} = 25°C$.
Next, calculate the range of temperature for Day 3:
$\text{Range} = \text{Maximum temperature} – \text{Minimum temperature} = 28 – 14 = 14°C$.
Finally, find the difference between the two results:
$25°C – 14°C = 11°C$.

Key Concept: Mean Daily Temperature Calculation

c) 28°C
[Solution Description]
The formula for mean daily temperature is:
$\text{Mean daily temperature} = \frac{\text{Maximum temperature} + \text{Minimum temperature}}{2}$
Plugging in the values:
$\text{Mean daily temperature} = \frac{34 + 22}{2} = \frac{56}{2} = 28^{\circ}C$
So, the mean daily temperature is $28^{\circ}C$.

Key Concept: Maximum and Minimum Thermometers, Range of Temperature

a) Day with max 30°C and min 15°C
[Solution Description]
Calculate the range for each day:
Day 1: $30 – 15 = 15°C$
Day 2: $31 – 17 = 14°C$
Day 3: $32 – 18 = 14°C$
Day 4: $30 – 17 = 13°C$
Day 5: $28 – 14 = 14°C$
The highest range is 15°C on Day 1.

Key Concept: Temperature Range Calculation

c) $14^\circ C$
[Solution Description]
The range of temperature is calculated as the difference between the maximum and minimum temperatures: $32^\circ C – 18^\circ C = 14^\circ C$.

Key Concept: Maximum and Minimum Thermometers

c) Maximum and minimum thermometer
[Solution Description]
A maximum and minimum thermometer is specifically designed to record the highest and lowest temperatures over a period, usually 24 hours.

Key Concept: Maximum and Minimum Thermometers

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that a maximum-minimum thermometer uses a liquid that expands when heated to record temperature extremes. This is true as these thermometers typically use alcohol or mercury, which expand with increasing temperature. The reason explains that the expansion pushes markers to indicate high and low temperatures, which stay in position until manually reset. Both statements are factually correct, and the reason accurately describes how the mechanism operates based on the assertion.

Key Concept: Mean Daily Temperature

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
Given:
Maximum temperature on 03.03.2025 = 32°C
Minimum temperature on 03.03.2025 = 18°C
Step 1: Apply the mean daily temperature formula.
$\text{Mean daily temperature} = \frac{32 + 18}{2} = \frac{50}{2} = 25^\circ C$
Step 2: Compare with Assertion (A).
The assertion states that the mean daily temperature is 25°C, which matches our calculation.
Step 3: Evaluate Reason (R).
The reason correctly provides the formula used to derive the mean daily temperature, and it justifies the assertion.
Conclusion: Both Assertion (A) and Reason (R) are true, and Reason (R) explains Assertion (A).

Key Concept: Anemometer Functionality

c) The wind speed is fast.
[Solution Description]
An anemometer measures wind speed by counting rotations per unit time. More rotations indicate faster wind speeds. Here, 120 rotations per minute suggest a relatively strong wind, but the exact speed cannot be determined without calibration data.

Key Concept: Wind Direction Measurement

d) Wind vane
[Solution Description]
The wind vane (or weather vane) rotates and points in the direction from which the wind is blowing. It has a pointer and a tail, allowing it to respond to even light breezes.

Key Concept: Wind and Wind Measurement

c) Assertion is true, but Reason is false.
[Solution Description]
The syllabus states that wind is indeed the movement of air from high-pressure to low-pressure areas, so the Assertion (A) is true. However, a wind vane measures the direction of the wind, not its speed. The speed is measured by an anemometer, which counts rotations to calculate speed in km/h. Thus, Reason (R) is false.

Key Concept: Wind impact, Multi-concept analysis

c) High wind speed and low humidity
[Solution Description]
High wind speeds increase evaporation rates, removing moisture from the soil. Combined with already low humidity (dry air), this accelerates soil drying. High pressure systems often bring dry weather due to descending air, reducing rainfall probability and exacerbating drought.

Key Concept: Wind speed calculation, Pressure gradient effect

c) The pressure gradient increases to 12 hPa over 100 km
[Solution Description]
The rotational speed of an anemometer is directly proportional to wind speed, which in turn depends on the pressure gradient. A higher rotation speed implies stronger wind caused by a steeper pressure gradient. The initial rotation speed was 120 rpm, and it increased to 180 rpm, indicating higher wind speed. Therefore, the pressure gradient must have increased proportionally.

Key Concept: Wind Speed Measurement

c) Wind speed
[Solution Description]
An anemometer measures wind speed using rotating cups that spin faster as the wind blows stronger. A meter counts the number of rotations and calculates the wind speed in $km/h$.

Key Concept: Wind Measurement and Direction

d) Assertion is false, but Reason is true.
[Solution Description]
The Assertion states that a wind vane measures wind speed, but this is incorrect. A wind vane measures wind direction, not speed. The Reason mentions the rotation of cups, which refers to an anemometer, not a wind vane. Therefore, the Assertion is false, but the Reason is true (though it describes an anemometer, not a wind vane).

Key Concept: Wind direction, Practical application

c) Southwest-northeast
[Solution Description]
A wind sock points downwind (i.e., in the direction the wind is blowing). Since it points northeast, the wind is coming from the southwest. To land against the wind, the runway should be aligned with the wind direction (southwest-northeast) so the aircraft lands heading into the southwest wind.

Key Concept: Wind Direction and Speed, Anemometer

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that the rotation speed of the anemometer’s cups is directly proportional to the wind speed. This is true because the stronger the wind, the faster the cups rotate due to increased force exerted by the wind. The reason explains how wind speed is calculated using the anemometer: by counting the number of rotations in a given time period and converting it into wind speed units like km/h. Since the reason correctly explains the relationship described in the assertion, both are true, and the reason justifies the assertion.

Key Concept: Wind Vane Usage

c) To determine the wind direction for safe flight operations.
[Solution Description]
A wind sock indicates wind direction, which is crucial for pilots during takeoff and landing to ensure safe operations by aligning aircraft movements with wind direction.

Key Concept: Wind Direction and Pressure

c) The pressure in the north is higher than the pressure at the field.
[Solution Description]
Wind moves from high-pressure areas to low-pressure areas. If the wind is blowing from the north towards the field, it means the pressure in the north is higher than the pressure at the field’s location.

Key Concept: Wind Movement Basics

c) To equalize pressure differences
[Solution Description]
Wind moves from high-pressure to low-pressure areas because air naturally flows from regions of higher density (high pressure) to regions of lower density (low pressure) to balance the atmospheric pressure.

Key Concept: Humidity, Precipitation

c) Sleet
[Solution Description]
High relative humidity (95\%) indicates abundant moisture in the air. When temperatures drop below freezing, this moisture condenses and freezes, leading to sleet (partly frozen rain) or hail (hard balls of ice). Given the high humidity and freezing conditions, sleet is the most probable form of precipitation.

Key Concept: Automated Weather Station, Disaster preparedness

b) To provide early warnings for Glacial Lake Outburst Floods (GLOFs)
[Solution Description]
Glacial lakes at high altitudes pose risks of Glacial Lake Outburst Floods (GLOFs), which can be triggered by sudden weather changes. An AWS provides real-time data on temperature, precipitation, and atmospheric pressure, enabling early warnings for potential GLOFs. This helps authorities take preventive measures and evacuate vulnerable areas.

Key Concept: Modern Meteorology

b) It provides more accurate and standardized measurements
[Solution Description]
Modern meteorology uses scientific instruments and data analysis to provide precise and reliable weather forecasts, unlike traditional methods that rely on observational cues with limited accuracy.

Key Concept: Elements of Weather

c) Cloud color
[Solution Description]
The elements of weather include temperature, precipitation, atmospheric pressure, wind, and humidity. The option that is not part of these elements is “Cloud color,” as it is not directly used to measure or define weather conditions.

Key Concept: Weather Predictions and Disaster Preparedness

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The Assertion states that accurate weather predictions help in resource mobilization by local governments, which is true as per the syllabus (“Accurate weather predictions help us prepare for extreme events and enable local governments to mobilize resources”). The Reason explains that forecasts provide advance warnings for events like cyclones, which is also true (“Example: Fishermen are warned about stormy weather at sea, or coastal areas are evacuated ahead of cyclones”). Moreover, the Reason correctly justifies the Assertion because advance warnings (Reason) directly facilitate resource mobilization (Assertion). Therefore, both are true, and the Reason explains the Assertion.

Key Concept: Importance of Measuring and Predicting Weather

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that accurate weather predictions help in evacuating coastal areas before a cyclone, which is true as per the syllabus. The reason states that cyclones can cause severe damage if not predicted in advance, which is also true. Moreover, the reason correctly explains why it is important to predict cyclones and evacuate areas, making the explanation valid.

Key Concept: Traditional Methods

b) Ants carrying eggs to higher ground
[Solution Description]
Traditional methods rely on observing natural indicators such as ants carrying eggs, frogs croaking loudly, or birds flying low, which signal impending rain or storms.

Key Concept: Weather prediction, Traditional indicators

c) Impending rainfall or storm
[Solution Description]
Traditional indicators like ants carrying eggs and frogs croaking loudly are associated with increased humidity and impending rainfall. These signs suggest that a rain or storm is likely to occur soon. Fishermen should avoid venturing into the sea during such conditions as storms can be dangerous.

Key Concept: Weather Prediction Importance

c) To warn them about storms and avoid going to sea
[Solution Description]
Accurate weather predictions help fishermen by warning them about dangerous conditions like storms at sea. This allows them to avoid venturing out when it is unsafe, thereby preventing potential disasters.

Key Concept: Disaster Preparedness

b) Ensures fishermen avoid venturing into stormy seas
[Solution Description]
Accurate weather predictions help coastal communities prepare for extreme events like cyclones, enabling timely evacuations and resource allocation. This minimizes potential loss of life and property damage.

Key Concept: Weather Prediction, Traditional Methods

d) Assertion is false, but Reason is true.
[Solution Description]
The assertion states that the behavior of ants carrying eggs is a reliable indicator for predicting rainfall in modern meteorology. However, this is false because modern meteorology relies on precise instruments like AWS (Automated Weather Stations) and scientific data analysis rather than traditional methods. The reason states that traditional weather prediction methods are based on long-term observations of natural phenomena and have been validated scientifically, which is true. Some traditional methods do have scientific backing, but they are not used as primary tools in modern meteorology. Therefore, while the Reason is true, the Assertion is false.

Key Concept: Traditional Weather Prediction

b) Observing natural signs and using regional sayings
[Solution Description]
In many parts of India, elders observe natural signs and use regional sayings to forecast the arrival of the monsoon. This traditional knowledge is passed down through generations.

Key Concept: Elements of Weather

c) Humidity
[Solution Description]
The elements of weather include temperature, humidity, precipitation, wind, and atmospheric pressure. Humidity specifically measures the amount of water vapor present in the air.

Key Concept: Traditional Weather Prediction Methods

c) Observing frogs croaking loudly
[Solution Description]
The syllabus states that observing animals like frogs croaking is a traditional method to predict rain. This is an example of natural indicators used for weather forecasting historically.

Key Concept: Traditional Weather Prediction

b) Frogs croaking loudly
[Solution Description]
Traditional weather prediction methods include observing natural signs like frogs croaking loudly, birds flying low, ants carrying eggs to higher ground, and pine cones opening/closing due to humidity changes.

Key Concept: Importance of weather predictions, disaster preparedness

b) It enables timely evacuation and resource allocation
[Solution Description]
Accurate weather predictions allow local governments to mobilize resources and take preventive measures such as evacuations before a cyclone strikes. Coastal regions are highly vulnerable to cyclones due to high winds and storm surges, which can cause significant damage and loss of life if unprepared. Early warnings help mitigate risks effectively.

Key Concept: Importance of Weather Predictions

b) To avoid venturing into the sea during storms and ensure safety
[Solution Description]
Accurate weather predictions help fishermen avoid venturing into the sea during stormy conditions, ensuring their safety. This aligns with the syllabus point that mentions warnings for fishermen during rough sea conditions.

Key Concept: Traditional weather prediction methods, modern meteorology

d) Rain or storm
[Solution Description]
Traditional weather prediction methods involve observing natural signs such as frogs croaking loudly. This behavior is typically linked to impending rain or storms due to the increase in humidity and atmospheric pressure changes. Modern meteorology confirms that animals are sensitive to these environmental changes, making their behaviors reliable indicators of weather shifts.

Key Concept: Climate change impact, extreme weather events

d) By making droughts and floods more frequent
[Solution Description]
Climate change has led to more frequent and intense extreme weather events such as droughts, floods, and cyclones. Predicting these events accurately has become crucial for preparedness, minimizing damage, and saving lives. Governments and communities rely on advanced meteorological data to respond effectively to these heightened risks.

Key Concept: Disaster Preparedness

b) Mobilize resources and take preventive measures
[Solution Description]
Accurate weather predictions help local governments take preventive actions and mobilize resources before extreme weather events occur. This includes evacuating coastal areas during cyclones or warning fishermen about storms.

Key Concept: Disaster Management, Modern Meteorology

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that accurate weather predictions are crucial for evacuating coastal areas ahead of cyclones, which is true as timely warnings save lives. The reason explains that modern meteorology uses scientific instruments to measure atmospheric pressure and wind speed, which is also true. Additionally, measuring these elements directly aids in cyclone prediction, making the reason a correct explanation of the assertion.

Key Concept: Importance of Weather Predictions

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that accurate weather predictions aid local governments in disaster preparedness, which is true as per the syllabus. The reason explains that precise forecasts allow efficient resource mobilization and evacuation plans, which is also true and directly supports the assertion by providing the mechanism through which predictions help governments.

Key Concept: Weather Elements Measured

d) Precipitation
[Solution Description]
Precipitation includes rain, snow, sleet, or hail falling from the sky. It directly helps predict rainfall or snowfall, as mentioned in the syllabus under “Weather Elements Measured for Predictions.”

Key Concept: Disaster Preparedness

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that weather predictions are crucial for evacuating coastal areas before a cyclone hits. This is true because timely forecasts allow authorities to take preventive measures. The reason given is that cyclones can cause severe damage to life and property, which is also true. Moreover, the reason correctly explains why early warnings (as mentioned in the assertion) are essential, as they help mitigate the impact of cyclones by enabling evacuation and resource mobilization. Thus, both the assertion and reason are true, and the reason is the correct explanation of the assertion.

Key Concept: Temperature Scales

c) 86°F
[Solution Description]
The formula to convert Celsius to Fahrenheit is $F = \frac{9}{5}C + 32$. Here, C = 30°C.
Step 1: Multiply 30 by $\frac{9}{5}$ which gives 54.
Step 2: Add 32 to 54 to get 86.
Therefore, 30°C equals 86°F.

Key Concept: Mean Daily Temperature

c) 24°C
[Solution Description]
Mean daily temperature is calculated using the formula:
$\text{Mean temperature} = \frac{\text{Maximum temperature} + \text{Minimum temperature}}{2}$
Given: Maximum temperature = $30°C$, Minimum temperature = $18°C$.
Step 1: Add the two temperatures:
$30 + 18 = 48$.
Step 2: Divide by $2$:
$\frac{48}{2} = 24°C$.
So, the mean daily temperature is $24°C$.

Key Concept: Mean Temperature Calculation

c) 30°C
[Solution Description]
The mean daily temperature is calculated using the formula $\text{Mean daily temperature} = \frac{\text{Maximum temperature} + \text{Minimum temperature}}{2}$.
Step 1: Add the maximum and minimum temperatures: $35 + 25 = 60$.
Step 2: Divide 60 by 2 to get the mean temperature: $\frac{60}{2} = 30$°C.
Therefore, the mean daily temperature is 30°C.

Key Concept: Temperature Scales

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that both Celsius and Fahrenheit scales measure the same physical quantity, which is true as they both represent temperature but use different units. The reason provides the correct mathematical relationship between Fahrenheit (\$) and Celsius (\$), confirming it is the correct explanation of the assertion.

Key Concept: Temperature range, Unit conversion

c) 40°F
[Solution Description]
Find max weekly temp (33°C) and min weekly temp (11°C). Range in Celsius is $33 – 11 = 22^\circ C$. Convert range to Fahrenheit: Since 1°C range equals 1.8°F range, $22 \times 1.8 = 39.6^\circ F \approx 40^\circ F$.

Key Concept: Temperature Range

b) 20°C
[Solution Description]
The range of temperature is calculated as the difference between the maximum and minimum temperatures.
Step 1: Subtract the minimum temperature from the maximum temperature: $40 – 20 = 20$°C.
Therefore, the range of temperature is 20°C.

Key Concept: Celsius to Fahrenheit Conversion

c) 77°F
[Solution Description]
To convert Celsius to Fahrenheit, use the formula:
$F = \left( C \times \frac{9}{5} \right) + 32$
Here, $C = 25°C$.
Step 1: Multiply $25$ by $\frac{9}{5}$:
$25 \times \frac{9}{5} = 45$.
Step 2: Add $32$ to the result:
$45 + 32 = 77°F$.
So, $25°C$ is equal to $77°F$.

Key Concept: Temperature Conversion, Mean Daily Temperature

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
\textbf{Step 1}: Calculate the equivalent of 22\textdegree C in Fahrenheit using the given formula.
$F = \left(\frac{9}{5} \times 22\right) + 32$
$F = \left(39.6\right) + 32 = 71.6\textdegree F$
The Assertion states that 22\textdegree C is equivalent to 71.6\textdegree F, which matches our calculation. Hence, the Assertion is true.
\textbf{Step 2}: The Reason provides the correct conversion formula from Celsius to Fahrenheit, and it accurately explains how the Assertion was derived. Therefore, both Assertion and Reason are true, and Reason correctly explains the Assertion.

Key Concept: Temperature Conversion

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
To verify the assertion, we will use the given conversion formula from Fahrenheit ($F$) to Celsius ($C$):
$C = \frac{5}{9}(F – 32)$
Substituting $F = 68^\circ F$:
$C = \frac{5}{9}(68 – 32) = \frac{5}{9} \times 36 = 20^\circ C$
The calculation confirms that $68^\circ F$ equals $20^\circ C$, so the Assertion is true. The Reason provides the correct formula for converting Fahrenheit to Celsius and is also true. Since the Reason correctly explains why the Assertion is valid, both statements are true, and the Reason is the correct explanation of the Assertion.

Key Concept: Celsius-Fahrenheit conversion, Mean daily temperature

c) 68°F
[Solution Description]
First calculate mean daily temperature in Celsius: $\frac{28 + 12}{2} = 20^\circ C$. Then convert to Fahrenheit using the formula $F = \frac{9}{5}C + 32$. So $\frac{9}{5} \times 20 + 32 = 36 + 32 = 68^\circ F$.

Key Concept: Comparative temperature analysis

c) City Y experiences greater temperature fluctuations
[Solution Description]
Both cities have same mean in Fahrenheit: $\frac{9}{5} \times 25 + 32 = 77^\circ F$. City X range is $10 \times 1.8 = 18^\circ F$, City Y range is $20 \times 1.8 = 36^\circ F$. City Y has more variable temperatures despite same mean.

Key Concept: Temperature Range

c) 12°C
[Solution Description]
The range of temperature is calculated as:
$\text{Range} = \text{Maximum temperature} – \text{Minimum temperature}$
Given: Maximum temperature = $36°C$, Minimum temperature = $24°C$.
Step 1: Subtract the minimum from the maximum:
$36 – 24 = 12°C$.
So, the temperature range is $12°C$.

Key Concept: Elements of Weather

d) Plant growth rate
[Solution Description]
Elements of weather include temperature, precipitation, humidity, wind, and atmospheric pressure. Plant growth rate is not an element of weather but can be influenced by it.

Key Concept: Weather Elements

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.
[Solution Description]
The assertion states that the troposphere is where all weather phenomena occur, which is true as per the syllabus. The reason explains why the troposphere varies in thickness, with it being thicker in tropical zones due to warm air expansion, which is also correct. However, while both statements are true, the reason does not directly explain why weather phenomena occur in the troposphere but rather describes its varying thickness. Therefore, the reason is not the correct explanation of the assertion.

Key Concept: Definition of Weather

b) The state of the Earth’s atmosphere at a particular time and place
[Solution Description]
The weather is defined as the state of the Earth’s atmosphere at a particular time and place. It includes elements like temperature, precipitation, wind, humidity, and atmospheric pressure.

Key Concept: Weather, Atmosphere, Troposphere

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.
[Solution Description]
The assertion claims that the troposphere is where all weather phenomena occur because of the high concentration of greenhouse gases. While it is true that the troposphere is where weather occurs, the reason provided (its proximity to the Earth’s surface and interaction with it) is correct but does not explain the assertion about greenhouse gases. Greenhouse gases are indeed present in the troposphere, but they are not the primary reason why weather occurs there; rather, the interaction between the Earth’s surface and the atmosphere (like heat exchange and water vapor) drives weather phenomena.
Therefore, both the assertion and reason are true, but the reason does not correctly explain the assertion.

Key Concept: Definition of Weather

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that the troposphere is the layer where all weather phenomena occur, which is correct as per the syllabus. The reason states that the troposphere is the closest layer to the Earth’s surface and contains most of the water vapor, which is also true. Furthermore, the presence of water vapor in the troposphere directly contributes to weather phenomena like precipitation, humidity, and storms, making the reason a correct explanation of the assertion.

Key Concept: Troposphere

c) Troposphere
[Solution Description]
The troposphere is the lowest layer of the Earth’s atmosphere where most weather phenomena, including clouds, rain, and storms, occur.

Key Concept: Atmospheric Pressure, Temperature

c) It decreases to 89°C
[Solution Description]
Boiling point depends on atmospheric pressure. Lower pressure means water molecules need less energy to escape into the vapor phase, so the boiling point decreases. At 700 hPa, the boiling point of water is approximately 89°C (from standard pressure-temperature tables).

Key Concept: Components of Weather

c) Troposphere
[Solution Description]
The troposphere is the layer of the Earth’s atmosphere closest to the surface, extending from 6 to 18 kilometers above ground level. This is where most weather phenomena take place.

Key Concept: Weather vs Climate

b) Weather is measured in days; climate is measured in years.
[Solution Description]
Weather refers to short-term atmospheric conditions in a specific area, while climate describes long-term patterns of weather over a significant period.

Key Concept: Wind, Precipitation

c) Moisture-laden air condenses on the windward side
[Solution Description]
Windward slopes face the incoming moist air masses. As the air rises over the mountain, it cools adiabatically, leading to condensation and precipitation. On the leeward side, the descending air warms up and becomes drier, resulting in less precipitation (rain shadow effect). This is a fundamental concept in orographic precipitation.

Key Concept: Elements of Weather

a) Altitude
[Solution Description]
The elements of weather are temperature, precipitation, atmospheric pressure, wind, and humidity. Among the given options, the one that does not fit as an element of weather must be identified.

Key Concept: Temperature, Humidity, Atmospheric Pressure

c) 100\%
[Solution Description]
First, understand that absolute humidity remains constant while relative humidity changes with temperature. At 25°C, if the relative humidity is 80\%, it means the air contains 80\% of the maximum water vapor it can hold at that temperature. When the temperature drops to 15°C, the capacity of air to hold water vapor decreases, increasing the relative humidity. Using the saturation vapor pressure curves, we conclude the new relative humidity will be higher than 80\%.
Calculation: Suppose the saturation vapor pressure at 25°C is 31.67 hPa. The actual vapor pressure = 80\% of 31.67 hPa = 25.34 hPa. Now, the saturation vapor pressure at 15°C is 17.05 hPa. The new relative humidity = (25.34 / 17.05) × 100 ≈ 148.6\%, but since relative humidity cannot exceed 100\%, the answer is 100\%.

Key Concept: AWS advantages, multi-step reasoning

c) AWS captures rapid changes, improving short-term forecast precision
[Solution Description]
Thunderstorms develop quickly, and frequent data updates (every 15 minutes) allow meteorologists to track rapid changes in atmospheric pressure, wind speed, and precipitation. Manual recordings every 6 hours miss critical fluctuations, reducing forecast accuracy.

Key Concept: AWS Location

c) At a glacial lake in Sikkim
[Solution Description]
The National Disaster Management Authority set up an AWS at a glacial lake in Sikkim at an altitude of more than 4800 metres above sea level.

Key Concept: Atmospheric Pressure

c) On top of a mountain
[Solution Description]
The question relates to atmospheric pressure variations. The syllabus states that atmospheric pressure decreases as altitude increases, so it would be lowest at high altitudes like mountains.

Key Concept: AWS components, disaster management

b) Alerting local authorities and initiating evacuation protocols
[Solution Description]
The AWS measures precipitation and wind speed to provide early warnings for floods. Detecting unusual increases suggests imminent flooding. The priority is to alert local authorities and evacuate vulnerable areas to minimize human and economic losses.

Key Concept: Weather Data Collection

c) Precipitation
[Solution Description]
The question is about the weather data collected by a rain gauge. From the syllabus, a rain gauge measures precipitation.

Key Concept: AWS Instruments

b) Anemometer
[Solution Description]
The question asks about the instrument used to measure wind speed and direction in an AWS. According to the syllabus, an anemometer measures wind speed and direction.

Key Concept: Automated Weather Station Sensors

d) Soil pH
[Solution Description]
An AWS measures weather parameters such as temperature, humidity, wind speed and direction, precipitation, and atmospheric pressure. Soil pH is not a standard parameter measured by AWS.

Key Concept: Automated Weather Stations, Weather Data Recording

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The Assertion states that AWS are essential for real-time weather data in remote areas. This is true because AWS can operate autonomously, making them ideal for locations where manual monitoring is impractical. The Reason claims that AWS eliminates human intervention for continuous data accuracy, which is also true. Moreover, the Reason correctly explains why AWS is effective in harsh or remote environments, as it removes human limitations and errors.

Key Concept: AWS Applications

d) Fashion design
[Solution Description]
AWS is widely used in agriculture, aviation, navigation, and environmental monitoring. Fashion design does not rely on weather data collected by AWS.

Key Concept: AWS: automatic recording of weather data

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that an AWS can measure multiple weather parameters without human intervention, which is true as per the syllabus description of AWS. The reason explains that AWS uses various sensors for automatic recording, which is also true and directly explains why AWS can function without human intervention. Thus, both the assertion and reason are correct, and the reason properly explains the assertion.

Key Concept: Automated Weather Station

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that AWS can provide weather data from remote locations autonomously, which is correct as per the syllabus example of AWS being installed at 4800m altitude in Sikkim. The reason explains this capability by mentioning the use of sensors for automatic recording, which is also true and directly explains why AWS can operate independently in harsh environments. Both statements are factually accurate, and the reason correctly justifies the assertion.

Key Concept: AWS placement, environmental monitoring

b) Wind resistance and corrosion-resistant materials
[Solution Description]
Coastal cyclones involve high winds and saltwater exposure. The AWS must withstand these harsh conditions to ensure durability and consistent data accuracy. Wind resistance and corrosion protection are therefore the most critical factors.

Key Concept: Basic Definition

c) To present the topic and purpose clearly
[Solution Description]
The introduction serves to present the main topic, provide background information, and state the thesis or purpose of the paper. It does not summarize findings or list references.

Key Concept: Assertion-Reason

c) Assertion is true, but Reason is false.
[Solution Description]
Solution cannot be provided as the syllabus is empty.

Key Concept: Basic Concept

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The Assertion states that the sky appears blue during the day, which is a scientifically accepted fact. The Reason explains that scattering of sunlight by air molecules (Rayleigh scattering) causes this phenomenon. Since both statements are correct and the Reason explains the Assertion, the correct answer is option (a).

Key Concept: Functionality

c) Overly technical jargon
[Solution Description]
An introduction should avoid overly complex arguments or excessive details, as its purpose is to introduce the topic clearly. References and methodology belong in later sections.

Key Concept: Concept

c) It is used to denote an unknown quantity in equations.
[Solution Description]
Since the syllabus is empty, this is a placeholder question. A correct answer would depend on the actual syllabus content.

Key Concept: Concept

b) They provide clarity and basis for future concepts.
[Solution Description]
Without syllabus content, this serves as a placeholder. The solution would depend on the subject’s introductory definitions.

Key Concept: Key Component

b) Thesis statement
[Solution Description]
A good introduction includes a clear thesis statement that outlines the main argument or focus of the paper. Appendices and detailed analysis are not part of the introduction.

Key Concept: Critical Thinking

c) It allows objective analysis and evaluation of evidence
[Solution Description]
Critical thinking is essential in research because it enables individuals to analyze information objectively, evaluate evidence, and draw reasoned conclusions. It helps in distinguishing between credible sources and biases.

Key Concept: Basic Concepts

b) To present the main idea and engage the reader
[Solution Description]
The primary purpose of an introduction in academic writing is to present the main idea or argument of the work, provide necessary background information, and engage the reader. It sets the stage for the rest of the document by outlining its scope and objectives.

Key Concept: Communication

b) Conveying a message clearly and ensuring understanding
[Solution Description]
Effective communication involves clearly conveying a message so that it is understood as intended. This includes active listening, clarity in expression, and appropriate feedback mechanisms.

Key Concept: No Syllabus Provided

d) Assertion is false, but Reason is true.
[Solution Description]
Since the syllabus is empty, no questions can be formulated without conceptual context.

Key Concept: Concept

c) To introduce the topic and outline key points.
[Solution Description]
This is a generic placeholder due to missing syllabus details. The solution would align with standard academic practices.

Key Concept: Rain Gauge Measurement

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that a rain gauge measures the height of water collected in millimeters to determine rainfall, which is true as per the syllabus description. The reason states that the scale attached to the cylinder provides a direct reading of the depth of rainwater, which is also correct and explains how the measurement is obtained using the rain gauge. Therefore, both assertion and reason are true, and the reason correctly explains the assertion.

Key Concept: Types of Precipitation

c) Hail
[Solution Description]
Precipitation includes various forms like rain, snow, sleet, and hail. Hail specifically refers to small, hard balls of ice that fall from the sky during thunderstorms.

Key Concept: Rain Gauge Measurement

c) The area received 15 mm of rainfall
[Solution Description]
The rain gauge measures rainfall by collecting water in a cylinder with a measuring scale. The height of the collected water represents the amount of rainfall. Here, 15 mm means the area received 15 mm of rainfall over 24 hours.

Key Concept: Rain gauge measurement

c) The height of the rainwater collected is 30 mm.
[Solution Description]
A rain gauge measures the depth of rainwater collected in its cylinder. If the scale shows 30 mm, it means the height of the water collected is 30 mm, indicating that the area received 30 mm of rainfall. The measurement is direct and does not involve any conversion or additional steps.

Key Concept: Precipitation Measurement, Data Interpretation

Correct Answer: b) 5 mm/hour (Moderate rainfall)
[Solution Description]
First, calculate the average rainfall intensity:
$\text{Average Intensity} = \frac{\text{Total Rainfall}}{\text{Time}} = \frac{30\,\text{mm}}{6\,\text{hours}} = 5\,\text{mm/hour}$
Moderate rainfall typically ranges between 2.5 mm/hour to 7.6 mm/hour. Thus, 5 mm/hour falls within the moderate range. The correct answer reflects this calculation and classification.

Key Concept: Rain gauge measurement, Precipitation calculation

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that if a rain gauge collects water to a depth of 20 mm over a 24-hour period, the recorded rainfall for that day is 20 mm. This is correct because the rain gauge measures the depth of rainwater collected, and the scale attached to the cylinder directly gives the rainfall amount in millimeters.
The reason states that the depth of water collected in the rain gauge’s measuring cylinder directly corresponds to the amount of rainfall received. This is also true as the design of the rain gauge ensures that the funnel collects rainwater and directs it into the measuring cylinder, where the depth is read off the scale to determine rainfall.
Moreover, the reason correctly explains the assertion because it describes how the measurement process works in the rain gauge, linking the collected water depth directly to the rainfall amount.

Key Concept: Rain Gauge Setup, Precipitation Variability

Correct Answer: c) The week had intermittent rainfall with significant variability.
[Solution Description]
Analyzing the data:
– Rainfall occurred on 4 out of 7 days (non-zero values).
– Highest single-day rainfall: 12 mm.
– Total weekly rainfall: 5 + 0 + 12 + 0 + 3 + 8 + 0 = 28 mm.
Valid conclusions must align with actual data trends, such as variability and total accumulation. The correct answer highlights the irregular distribution of rainfall.

Key Concept: Types of precipitation

c) Frozen or partly frozen rain.
[Solution Description]
Sleet is defined as frozen or partly frozen rain, according to the syllabus. It is different from hail, which consists of small, hard balls of ice. This question tests basic recall of key terms related to precipitation.

Key Concept: Rain Gauge Placement

c) To ensure accurate measurement of rainfall
[Solution Description]
Placing a rain gauge in an open area ensures accurate measurement. Obstructions can block rainfall or cause uneven collection due to wind or runoff, leading to incorrect readings.

Key Concept: Precipitation Measurement, Rain Gauge Setup

Correct Answer: c) The tree blocked some rainwater from reaching the gauge.
[Solution Description]
The rain gauge near the tall tree may have been obstructed by the tree’s canopy, causing some rainwater to be blocked or diverted. This results in lower measurements compared to the unobstructed gauge in the open field. The correct answer is the option explaining obstruction due to nearby objects.

Key Concept: Placement of rain gauge

c) Open ground with elevated platform.
[Solution Description]
A rain gauge should be placed in an open area away from obstructions like trees or buildings to ensure accurate measurement of rainfall. It should also be on a flat surface to prevent tilting. Among the options, an open ground with an elevated platform is ideal as it avoids obstructions and provides stability.

Key Concept: Rain Gauge Measurement

d) Assertion is false, but Reason is true.
[Solution Description]
The assertion states that if a rain gauge collects 10 mm of water, the area received 10 cm of rainfall. This is incorrect because the depth of rainwater measured (10 mm) directly represents the rainfall in millimeters, not centimeters. The reason correctly explains that the depth of water collected in the measuring tube equals the rainfall received by the area, but it does not explain the wrong conversion in the assertion. Therefore, the assertion is false, and the reason is true.

Key Concept: Atmospheric Pressure, Precipitation

c) Decreasing pressure enhances upward air currents and condensation
[Solution Description]
Cyclones are associated with low-pressure systems where rising warm air cools rapidly, causing condensation and heavy precipitation. The pressure drop (1013→980 hPa) indicates strong upward air motion, which leads to cloud formation and rainfall (150 mm). The correct relationship is that falling pressure intensifies upward air movement, resulting in heavier precipitation.

Key Concept: Weather Elements

d) Assertion is false, but Reason is true.
[Solution Description]
The assertion states that the troposphere is thicker at the poles than in the tropical zone. However, from the syllabus, it is mentioned that the troposphere is “less thick at the poles (where the cold air contracts) and thicker in the tropical zone (where the warmer air expands).” This means the Assertion is false. The Reason correctly explains why the troposphere is less thick at the poles due to cold air contracting, so the Reason is true. Therefore, the correct answer is that the Assertion is false, but the Reason is true.

Key Concept: Temperature

c) Temperature perception varies based on acclimatization to local weather conditions
[Solution Description]
Temperature perception is relative and depends on what people are accustomed to in their local climate. Krishnan feels chilly at 20°C because Chennai usually has higher temperatures, so 20°C is cold for him. In contrast, Kashmir generally has lower temperatures, making 20°C seem pleasant for Amir.

Key Concept: Humidity

c) Humidity
[Solution Description]
According to the syllabus, a hygrometer measures humidity, which is the amount of water vapor in the air. This is clearly stated in the instrument-weather element table.

Key Concept: Temperature, Humidity, Wind

c) Inland humidity increases as moist air mixes with drier air
[Solution Description]
Relative humidity depends on both temperature and moisture content. Coastal air at 30°C holds more moisture due to higher initial humidity (80\%). When this moist air moves inland at the same temperature but higher pressure conditions, the moisture capacity remains constant, thus maintaining high humidity. However, inland’s lower original humidity suggests drier conditions, so mixing would increase humidity there. The correct answer is that inland humidity increases.

Key Concept: Atmospheric Pressure

c) It decreases because there’s less air pushing down from above
[Solution Description]
Atmospheric pressure decreases with altitude because there is less air above you exerting pressure. As you climb a mountain, the air becomes thinner and pressure drops. This is why mountaineers need special equipment to breathe at high altitudes.

Key Concept: Precipitation

c) Sleet
[Solution Description]
Sleet is defined as frozen or partly frozen rain in the syllabus under “Definitions.” This matches the question directly.

Key Concept: Precipitation

b) Raindrops that freeze into ice pellets before reaching the ground
[Solution Description]
Sleet is a form of precipitation where raindrops freeze into ice pellets before reaching the ground. It occurs when snowflakes partially melt as they fall through a warm layer of air and then refreeze near the surface. This is different from hail, which forms in thunderstorms due to strong updrafts.

Key Concept: Precipitation, Atmospheric Pressure

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that heavy rainfall causes a drop in atmospheric pressure. This is true because during heavy rain, water occupies space in the atmosphere, displacing air molecules. The reason given is also correct as water droplets in precipitation reduce the density of the air column, thereby decreasing the weight of the air and consequently the atmospheric pressure. Moreover, the reason accurately explains the assertion since it directly links the displacement effect of precipitation to the drop in atmospheric pressure.

Key Concept: Weather Elements

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that temperature is measured using a thermometer, which is correct as per the syllabus. The reason explains what temperature represents, which is also accurate (“how hot or cold the atmosphere is”). Furthermore, the reason correctly justifies why we measure temperature, as knowing whether it is hot or cold is essential for understanding weather conditions. Thus, both assertion and reason are true, and the reason correctly explains the assertion.

Key Concept: Traditional Prediction, Wind

c) Moisture-bearing winds might arrive contrary to forecasts
[Solution Description]
Pine cones close when humidity is high to protect seeds, often indicating moist air. In dry forecasts, persistent closure suggests unexpected moisture-laden winds may arrive. Since traditional knowledge links such observations to changing wind patterns bringing humidity, the correct inference is that humid winds are likely approaching despite the dry forecast.

Key Concept: Temperature

c) Thermometer
[Solution Description]
A thermometer is the instrument used to measure how hot or cold the atmosphere is, which means it measures temperature. The syllabus explicitly mentions this in the table matching instruments with weather elements.

Key Concept: Traditional Weather Prediction

c) Birds flying low
[Solution Description]
Traditional methods of weather prediction include observing nature. Birds flying low indicates that rain might be approaching because the air pressure drops before rain, causing insects to fly lower, which in turn makes birds fly lower to catch them.

Key Concept: AWS, Atmospheric Pressure, Weather Prediction

b) Heavy snowfall and strong winds
[Solution Description]
The AWS recorded a low atmospheric pressure of 650 hPa at a high altitude. Generally, atmospheric pressure decreases with altitude. At sea level, standard pressure is 1013 hPa. Low pressure often indicates unstable weather conditions such as storms or heavy precipitation. Since this station is located in a glacial area, such low pressure could signal incoming severe weather like blizzards or strong winds.

Key Concept: Weather Stations

c) Weather station
[Solution Description]
A weather station brings together various instruments to measure and track weather conditions. Readings are taken regularly to help in mapping and forecasting.

Key Concept: Weather Monitoring and Prediction

a) Cloud cover
[Solution Description]
An Automated Weather Station (AWS) measures temperature, humidity, wind speed and direction, precipitation, and atmospheric pressure. It does not measure cloud cover, which is typically observed visually or via satellite imagery.

Key Concept: Elements of Weather

c) Soil type
[Solution Description]
Temperature, precipitation, atmospheric pressure, wind, and humidity are elements of weather. Soil type is not directly related to weather monitoring.

Key Concept: Automated Weather Station

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that AWS is important for accurate weather forecasting, which is true because they provide precise and timely data. The reason explains why AWS is important by listing the measurements it takes automatically, supporting the assertion directly. Therefore, both the assertion and reason are true, and the reason correctly explains the assertion.

Key Concept: Automated Weather Station

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that AWS provide more accurate weather predictions than traditional observation methods, which is true because AWS eliminate human error and collect real-time data continuously. The reason provided is that AWS use sensors to continuously measure and record multiple weather parameters without human intervention, which explains why the assertion is correct. Thus, both the assertion and reason are true, and the reason correctly explains the assertion.

Key Concept: Accurate Predictions

c) To avoid dangerous weather conditions at sea
[Solution Description]
Accurate weather predictions are crucial for fishermen to avoid dangerous conditions at sea, such as storms or cyclones, which can threaten their safety and livelihoods.

Key Concept: Humidity, Wind Speed, Traditional Indicators

d) Light to moderate rain with calm winds
[Solution Description]
Frogs croak loudly due to increased humidity before rain. The AWS confirms this with 95\% humidity, which is very high and typically precedes rain. However, the wind speed is low (5 km/h), suggesting that the rain might not be accompanied by strong winds. This combination indicates imminent rainfall without severe wind conditions.

Key Concept: Meteorology

c) Meteorology
[Solution Description]
The systematic study of weather and its evolution is called meteorology. It forms the basis for weather forecasting.

Key Concept: Automated Weather Station, Traditional Weather Prediction

d) Assertion is false, but Reason is true.
[Solution Description]
The Assertion states that AWS has completely replaced traditional weather prediction methods due to their accuracy and timeliness. While AWS provides highly precise and automated data collection, traditional methods are still used in certain regions where technological infrastructure is lacking or as supplementary indicators. Thus, the Assertion is false because both systems coexist rather than AWS entirely replacing traditional methods. The Reason correctly highlights the subjective nature and lower precision of traditional methods compared to instrument-based measurements, making it true. Therefore, Assertion is false, but Reason is true.

Key Concept: Temperature, Precipitation, Aviation Hazards

b) Icing on aircraft surfaces
[Solution Description]
Rapid temperature drop below freezing while precipitation is occurring indicates supercooled water droplets can freeze on aircraft surfaces, leading to icing. Icing increases aircraft weight and disrupts aerodynamics, making it extremely hazardous for aviation. Other options are less directly linked to the given conditions.

Key Concept: Natural Indicators of Weather

b) Heavy rainfall
[Solution Description]
Ants shifting their eggs to higher ground is a traditional sign of heavy rain approaching. This behavior helps protect their eggs from being flooded. Thus, the farmers should expect heavy rain.

Key Concept: Automated Weather Station, Natural Indicators, Predicting Disasters

b) Heavy rainfall is expected shortly.
[Solution Description]
Ants moving their eggs to higher ground and pine cones closing are natural indicators of imminent heavy rain. The drop in atmospheric pressure recorded by the AWS further confirms unstable weather conditions, typically leading to heavy precipitation. These signs collectively suggest that a heavy rainfall event is likely to occur soon.

Key Concept: Weather Monitoring Tools

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that a barometer reading below $1000 \, \text{mb}$ indicates stormy weather, which is true as per the syllabus. The reason explains that lower atmospheric pressure is linked to depressions or storms, which is also correct and directly explains why the assertion is true. Hence, both are true, and the reason correctly explains the assertion.

Key Concept: Atmospheric Pressure and Weather Prediction

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
[Solution Description]
The assertion states that a barometric pressure reading below $1000 \text{ mb}$ indicates stormy weather. According to the syllabus, normal atmospheric pressure at sea level is around $1013 \text{ mb}$, and a pressure below $1000 \text{ mb}$ indicates a depression, which is commonly associated with stormy or unstable weather conditions. Both the assertion and reason are true, and the reason correctly explains why low atmospheric pressure (depression) leads to stormy weather.

Key Concept: Meteorology, Weather Stations, Atmospheric Pressure

c) A cyclone or severe storm is likely approaching.
[Solution Description]
The normal atmospheric pressure at sea level is around $1013 \, \text{mb}$. A reading below $1000 \, \text{mb}$ indicates a depression, which often signifies stormy or cyclonic conditions. Here, the measured atmospheric pressure ($980 \, \text{mb}$) is significantly lower than $1000 \, \text{mb}$, suggesting an impending severe weather event like a cyclone or heavy storm.