# CBSE Worksheet for chapter-9 Wave Motion & Sound class 9

## Find CBSE Worksheet for chapter-9 Wave Motion & Sound class 9

CLASS-9

BOARD: CBSE

Physics Worksheet - 9

TOPIC: Wave Motion & Sound

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SUMMARY

• Wave motion, Classification of waves depending on medium & its direction of vibration
• Sound wave, Production of sound waves, Propagation of sound.
• Wave terminology, Range of hearing, Sonic boom.
• Reflection of sound, Speed of sound in different medium, Effect of temperature on speed of sound, Echo, Reverberation
• Audible, Ultrasonic and Infrasonic waves, Applications of ultrasound
• Sonar – Principle and working of sonar, The human ear

#### SECTION I – OBJECTIVE

1. What is velocity of sound in water at room temperature?
1. 1500 m/s
2. 330 m/s
3. 1500 km/s
4. 330 km/s
2. Pitch of high frequency sound is:
1. High
2. Low
3. Zero
4. Infinity
3. Voice of a friend is recognised by its:
1. Pitch
2. Quality
3. Intensity
4. Velocity
4. A sonar echo takes 4.4sec to return from a submarine. If the speed of sound in water is 1500m/s, then the distance of submarine from the sonar is:
1. 1500m
2. 3000m
3. 3300m
4. 3600m
5. When sound waves travelling in air enter into the medium of water, the quantity which remains unchanged is:
1. Wavelength
2. Velocity
3. Frequency
4. None
6. The velocity of sound in air at 300C is approximately:
1. 332 m/s
2. 350 m/s
3. 530 m/s
4. 332 km/s
7. Velocity of sound is maximum in
1. Iron
2. Mercury
3. Water
4. Air
8. The sound propagates in a gaseous medium by:
1. Transverse waves
2. Longitudinal waves
3. Both A and B
4. Neither A nor B
9. The frequency of a source of sound is 100 Hz. How many times does it vibrate in a minute?
1. 100
2. 1000
3. 600
4. 6000
10. Sound waves of wavelength ‘X’ travels from a medium in which their speed is V into a medium in which their speed is 4 V. The wavelength of sound in the second medium is:
1. X
2. 2X
3. 3X
4. 4X

#### SECTION II - SUBJECTIVE

1. Define the following terms related to sound waves:
1. Pitch
2. Loudness
3. Intensity
4. Quality
2. Distinguish between:
1. Mechanical wave & Non mechanical wave
2. Transverse wave &longitudinal wave
3. Define reverberation.
4. With the help of a suitable diagram explain the working of human ear.
5. Define the following:
1. Wave motion
2. Amplitude
3. Wavelength
4. Ultrasound.
6. Write any three applications of ultra sound.
7. A person has a hearing range from 20Hz to 20Khz. What are the typical wavelengths of sound waves in air corresponding to these two frequencies?(Speed of sound in air = 340m/s)
8. A submarine emits a sonar pulse which returns from the underwater cliff in 1.02 sec. If the speed of sound in salt water is 1531m/s, how far away is the cliff?

### Solutions: to worksheet-9 Wave Motion & Sound

#### Objective Problems:

 1.(A) 2.(A) 3.(B) 4.(C) 5.(C) 6.(B) 7.(A) 8.(B) 9.(D) 10.(D)

Subjective Problems :

1. 17m, 17mm
2. 780.8 m