CLASS: IX NCERT (CBSE)
PHYSICS
Sound
Question 1: When a wave travels through a medium ______.
1. particles are transferred from one place to another
2. energy is transferred in a periodic manner
3. energy is transferred at a constant speed
4. none of the above statements is applicable
Answer: 3
Question 2: The minimum distance between the source and the reflector, so that an echo is heard is approximately equal to ______.
1. 10 m
2. 17 m
3. 34 m
4. 50 m
Answer: 2
Question 3: Bats detect the obstacles in their path by receiving the reflected ______.
1. infrasonic waves
2. radio waves
3. electro-magnetic waves
4. ultrasonic waves
Answer: 4
Question 4: When sound travels through air, the air particles ______.
1. vibrate along the direction of wave propagation
2. vibrate but not in any fixed direction
3. vibrate perpendicular to the direction of wave propagation
4. do not vibrate
Answer: 1
Question 6: The frequency of a wave travelling at a speed of 500 ms-1 is 25 Hz. Its time period will be ______.
1. 20 s
2. 0.05 s
3. 25 s
4. 0.04 s
Answer: 4
Question 7: The amplitude of a wave is ______.
1. the distance the wave moves in one second
2. the distance the wave moves in one time period of the wave
3. the maximum distance moved by the medium particles on either side of the mean position
4. the distance equal to one wave length
Answer: 3
Question 8: Which of the following is not a characteristic of a musical sound?
1. Pitch
2. Wavelength
3. Quality
4. Loudness
Answer: 2
Question 9: Sound waves do not travel through
1. solids
2. liquids
3. gases
4. vacuum
Answer: 4
Question 10: The physical quantity, which oscillates in most waves, is
1. mass
2. energy
3. amplitude
4. wavelength
Answer: 3
Question 11: Sound waves are
1. longitudinal
2. transverse
3. partly longitudinal and partly transverse
4. sometimes longitudinal and sometimes transverse
Answer: 1
Question 12: The frequency which is not audible to the human ear is
1. 50 Hz
2. 500 Hz
3. 5000 Hz
4. 50000 Hz
Answer: 4
Question 13: The speed of sound in medium depends upon
1. amplitude
2. frequency
3. wavelength
4. properties of the medium
Answer: 4
Question 14: Which of the following will remain unchanged when a sound wave travels in air or in water?
1. Amplitude
2. Wavelength
3. Frequency
4. Speed
Answer: 3
Question 15: A sound source sends waves of 400 Hz. It produces waves of wavelength 2.5 m. The velocity of sound waves is
1. 100 m/s
2. 1000 m/s
3. 10000 m/s
4. 3000 km/s
Answer: 2
Question 16: The time period of a vibrating body is 0.05 s. The frequency of waves it emits is 1.5 Hz
2. 20 Hz
3. 200 Hz
4. 2 Hz
Answer: 2
Question 17: A source of frequency of 500 Hz emits waves of wavelength 0.4 m, how long does the waves take to travel 600 m?
1. 3 s
2. 6 s
3. 9 s
4. 12 s
Answer: 1
Question 18: Sound and light waves both
1. have similar wavelength
2. obey the laws of reflection
3. travel as longitudinal waves
4. travel through vacuum
Answer: 2
Question 19: The method of detecting the presence, position and direction of motion of distant objects by reflecting a beam of sound waves is known as _____.
1. RADAR
2. SONAR
3. MIR
4. CRO
Answer: 2
Question 20: The technique used by bats to find their way or to locate food is _______.
1. SONAR
2. RADAR
3. Echolocation
4. Flapping
Answer: 3
Question 21: An ultrasonic wave is sent from a ship towards the bottom of the sea. It is found that the time interval between the sending and receiving of the wave is 1.6 s. What is the depth of the sea, if the velocity of sound in the seawater is 1400 m/s?
1. 1120 m
2. 560 m
3. 1400 m
4. 112 m
Answer: 1
Question 22: An example for mechanical wave.
1. Radio wave
2. Light wave
3. Infrared radiation
4. Sound wave
Answer: 4
Question 23: Which of the following quantities is transferred during wave propagation?
1. Speed
2. Mass
3. Matter
4. Energy
Answer: 4
Question 24: If a vibrator strikes the water 10 times in one second, then the frequency of wave is _________.
1. 10 Hz
2. 0.5 Hz
3. 5 Hz
4. 0.1 Hz
Answer: 1
Question 25: Unit of wavelength is __________.
1. newton
2. erg
3. dyne
4. angstrom
Answer: 4
Question 27: SI Unit of time period is __________.
1. second
2. hour
3. minute
4. nanosecond
Answer: 1
Question 28: The vibrations or the pressure variations inside the inner ear are converted into electrical signals by the_________.
1. cochlea
2. tympanic membrane
3. pinna
4. anvil
Answer: 1
Question 29: Vibrations inside the ear are amplified by the three bones namely the _________ in the middle ear.
1. hammer, anvil and stirrup
2. hammer, anvil and pinna
3. hammer, cochlea and stirrup
4. auditory bone, anvil and stirrup
Answer: 1
Question 30: The persistence of audible sound due to the successive reflections from the surrounding objects even after the source has stopped to produce that sound is called _________.
1. reflection
2. echo
3. reverberation
4. rarefaction
Answer: 3
