Class 8 Science Chapter 10 Sound

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I. Chapter Summary:

This chapter explains the production, propagation, and properties of sound. It begins by describing how sound is produced through vibrations and how it travels through different mediums (solids, liquids, gases). It discusses frequency, amplitude, pitch, loudness, and time period of sound waves. The human ear’s structure and function are introduced, along with the concepts of noise vs musical sound, noise pollution, and measures to control noise pollution. The chapter emphasizes the importance of listening health and using sound responsibly in the environment.

II. Key Concepts Covered:

III. Important Questions:

(A) Multiple Choice Questions (1 Mark):

1. The unit of frequency is:
   a) Newton
   b) Joule
   c) Hertz ✔️
   d) Decibel

2. Sound cannot travel through:
   a) Solids
   b) Liquids
   c) Gases
   d) Vacuum ✔️

3. Pitch of a sound depends on:
   a) Amplitude
   b) Frequency ✔️
   c) Loudness
   d) Wavelength

4. Human ear can hear sounds between:
   a) 2–20 Hz
   b) 20–20,000 Hz ✔️
   c) 200–2,000 Hz
   d) 2,000–20,000 Hz

(B) Short Answer Questions (2/3 Marks):

1. What is sound? How is it produced? (PYQ 2020)

2. Define frequency and mention its SI unit.

3. What is noise pollution? Write two of its harmful effects. (PYQ 2019)

4. Why is the sound louder when we hit a drum harder?

(C) Long Answer Questions (5 Marks):

1. Explain how sound is produced and propagated through a medium. (PYQ 2021)

2. Differentiate between music and noise with examples.

3. What are the causes of noise pollution? Suggest four ways to control it.

4. Draw a neat labelled diagram of the human ear and explain its parts.

(D) HOTS (Higher Order Thinking Skills):

1. Why do astronauts use radios to talk in space even if they are close to each other?

2. Why do temples and railway stations have loudspeakers placed at heights?

IV. Key Formulas/Concepts:

V. Deleted Portions (CBSE 2025–2026):

No portions have been deleted from this chapter as per the rationalized NCERT textbooks.

VI. Chapter-Wise Marks Bifurcation (Estimated – CBSE 2025–2026):

VII. Previous Year Questions (PYQs):

VIII. Real-World Application Examples to Connect with Topics:

• Ultrasound used in medical diagnosis (sonography).

• Noise-cancelling headphones reduce background noise through wave cancellation.

• Soundproof rooms and theaters use absorption materials to block sound.

• Animals like dogs and bats can hear frequencies beyond human hearing range.

IX. Student Tips & Strategies for Success (Class-Specific):

Time Management:

• Allocate short weekly slots to practice formulas and auditory range facts.

• Use mnemonics to remember the structure of the ear and sound wave terms.

Exam Preparation:

• Revise all diagrams (especially waveform and human ear) for better recall.

• Focus on definitions + examples for music, noise, frequency, amplitude.

Stress Management:

• Avoid exposure to loud sounds for long durations.

• Practice breathing exercises if sensitive to noise in school settings.

X. Career Guidance & Exploration (Class-Specific):

For Class 9–10 Students:

Explore:

• NTSE, CBSE Science Exhibitions, Young Innovator Challenges, Music & Acoustics Clubs

XI. Important Notes:

• Understand the relationship between frequency and pitch, amplitude and loudness.

• Practice drawing and labeling the human ear.

• Always refer to ncert.nic.in and cbseacademic.nic.in for official updates.