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Sound

ICSE Grade 10 Physics - Chapter 7

📚 Smart Summary

1. Nature of Sound

Sound: A form of energy that produces the sensation of hearing. It is produced by vibrating objects.

Sound Waves: Longitudinal mechanical waves that require a medium (solid, liquid, or gas) to travel.

Characteristics: Compressions (high pressure regions) and rarefactions (low pressure regions).

Speed of Sound: Varies with medium and temperature. In air at 20°C, speed ≈ 343 m/s. Sound travels fastest in solids, slower in liquids, and slowest in gases.

2. Properties of Sound Waves

Frequency (f): Number of vibrations per second. Unit: Hertz (Hz).

Wavelength (λ): Distance between two consecutive compressions or rarefactions. Unit: meter (m).

Amplitude: Maximum displacement from the mean position. Determines loudness.

Wave Equation: v = f × λ, where v is the speed of sound.

Pitch: Depends on frequency. Higher frequency = higher pitch.

Loudness: Depends on amplitude. Greater amplitude = louder sound.

3. Reflection of Sound

Echo: Reflection of sound heard after a time interval. Minimum distance for echo = 17 m (in air).

Reverberation: Persistence of sound due to multiple reflections.

Applications: Sonar (Sound Navigation and Ranging), ultrasound imaging, echolocation.

📐 Formulas

Wave Equation: v = f × λ

Relates speed, frequency, and wavelength of sound waves.

Distance for Echo: d = (v × t) / 2

Calculates distance to reflecting surface using time taken for echo.

🎯 Test Your Knowledge

Multiple Choice Questions

1. Sound is a:

2. Sound cannot travel through:

3. The speed of sound is maximum in:

4. The pitch of sound depends on:

5. The loudness of sound depends on:

6. The minimum distance required to hear an echo in air is approximately:

7. SONAR uses:

8. The audible range of frequency for humans is:

9. Reverberation is caused by:

10. If the frequency of a sound wave is doubled, its wavelength:

Practice Numericals

Practice Problem 1: A sound wave has a frequency of 500 Hz and travels at 340 m/s. Calculate its wavelength in meters.

Practice Problem 2: An echo is heard after 2 seconds. If the speed of sound is 340 m/s, find the distance to the reflecting surface in meters.

Practice Problem 3: A sound wave has a wavelength of 0.85 m and frequency of 400 Hz. Calculate the speed of sound in m/s.

Practice Problem 4: A person claps near a cliff and hears the echo after 3 seconds. If the speed of sound is 330 m/s, how far is the cliff in meters?

Practice Problem 5: The time period of a sound wave is 0.002 seconds. Calculate its frequency in Hz.