CBSE Class 9 Science Sound MCQs

Question. You must have seen the doctor checking the sounds produced in the chest or heartbeat of a patient using a medical instrument called Stethoscope. On what principle does this Stethoscope work?
(a) Multiple refractions
(b) Multiple reflections
(c) Wave motion
(d) None of these

Answer : B

Question. The bats can fly in the darkness of night without colliding with the other objects by emitting special sounds while flying. Which characteristic of sound is used by the bats to navigate?
(a) Ultrasound
(b) Infrasound
(c) Audible sound
(d) None of these

Answer : A

Question. The sound can travel in air when:
(a) Particles of medium travel from one place to another
(b) There is no moisture in the atmosphere
(c) Disturbance travel from one place to another
(d) Both particles as well as disturbance travel from one place to another

Answer : C

Question. On increasing the temperature, the speed of sound in air:
(a) Increases
(b) Decreases
(c) Does not change
(d) First increases then becomes constant

Answer : A

Question  Loudness measures the sound energy reaching the ear per second and depends on the amplitude of the sound wave. What is the unit used to measure the loudness of sound?
(a) hertz
(b) decibel
(c) meter/second
(d) second

Answer : B

Question . We can distinguish between a man’s voice and a woman’s voice of the same loudness even without seeing them. This is due to a characteristic of sound which measures the shrillness of sounds. Can you choose the correct unit of the quantity on which this characteristic of sound depends?
(a) hertz
(b) meter/second
(c) meter
(d) unitless

Answer : A

Question . The sound can travel in air when:
(a) Particles of medium travel from one place to another
(b) There is no moisture in the atmosphere
(c) Disturbance travel from one place to another
(d) Both particles as well as disturbance travel from one place to another

Answer : C

Question. Which of the following can produce longitudinal as well as transverse waves under different conditions?
(a) Bats
(b) Slinky
(c) Tuning fork
(d) None of these

Answer : B

Question. The bats can fly in the darkness of night without colliding with the other objects by emitting special sounds while flying. Which characteristic of sound is used by the bats to navigate?
(a) Ultrasound
(b) Infrasound
(c) Audible sound
(d) None of these

Answer : A

Question. If the speed of a wave is 380 m/s and its frequency is 1900 Hz, then the wavelength of the wave will be:
(a) 20 m
(b) 0.2 m
(c) 200 m
(d) 2 m

Answer : B

Question. A key of mechanical piano is first struck gently and then struck again but much harder this time. What kind of change in sound will you observe in the second case:
(a) Sound will be louder but the pitch will not be different
(b) Sound will be louder and the pitch will also be higher
(c) Sound will be louder but the pitch will be lower
(d) Both loudness and pitch will remain unaffected

Answer : C

Question. On increasing the temperature, the speed of sound in air:
(a) Increases
(b) Decreases
(c) Does not change
(c) First increases then becomes constant

Answer : A