# Class 9 Physics Sound

Sound

Very Short Answer Type Questions (One Mark Each)

Q.1.   Can sound travel through vacuum ?

Answer Answer: No, sound cannot travel through vacuum.

Q.2.   What is the nature of sound waves ?

Answer Answer: Sound waves are longitudinal mechanical waves.

Q.3.   In which direction medium particles, oscillates in a longitudinal wave ?

Answer Answer: Parallel to the directions of wave motion.

Q.4.   What is a transverse wave ?

Answer Answer: A wave in which medium particles are oscillating along a direction perpendicular to the direction of wave motion.

Q.5.   Define frequency of a wave?

Answer Answer: The number of oscillation made by a medium particle in one second is called the frequency of wave.

Q.6.   Give a relation correlating sound velocity with its frequency and wavelength ?

Answer Answer: Velocity of sound (v) = frequency (f) x wavelength (λ)

Q.7.   A sound travels in air with a speed of 330 m/s. Find the wavelength of sound wave if its frequency is 500 Hz.

Answer Answer: Wavelength (λ) = Velocity of sound (v) / frequency (f) = 330/500 = 0.66 m

Q.8.   What is SI unit of frequency ?

Answer Answer: A hertz (Hz), where 1 Hz = 1 oscillation per second.

Q.9.   What is the true meaning of amplitude of a longitudinal wave ?

Answer Answer: Maximum variation of pressure (or density) in the given longitudinal wave.

Q.10.   How is the frequency of a wave related to its time period ?

Answer Answer: Frequency = 1 / Time period

Q.11.   Name the three characteristics of a sound.

Answer Answer: (i) pitch (ii) Loudness, and (iii) Quality

Q.12.   On which physical quantity does pitch of a sound depend ?

Answer Answer: Pitch solely depends on the frequency of sound.

Q.13.   In an orchestra different musical instruments produce their own sounds. Do these sounds reach us with same speed or different speed ? Why ?

Answer Answer: With same speed because speed of sound in a medium is same for sounds of all frequencies.

Q.14.   On what factors does the loudness of a sound depend?

Answer Answer: Loudness of a sound mainly depends on its amplitude and the response of the listener’s ear to the sound.

Q.15. Which sound has higher energy, a loud sound or a soft sound ?

Answer Answer: A loud sound has more energy associated with it.

Q.16.   What is the meaning of the characteristic ‘quality’ of a sound ?

Answer Answer: Quality is that characteristics which enables us to distinguish two different sounds although they may be having same pitch and same loudness.

Q.17.   On what factors does speed of sound in a medium depend ?

Answer Answer: Speed of sound in a medium depends on density and elasticity of the medium.

Q.18.   How does speed of sound in a medium vary on changing the temperature ?

Answer Answer: Speed of sound in a medium increases with increase in temperature.

Q.19.   How does speed of sound change when we go from solid to gaseous state ?

Answer Answer: The speed of sound decreases when we go from solid to gaseous state.

Q.20.   What is supersonic speed ?

Answer Answer: Supersonic speed means speed of an object greater than the speed of sound in air.

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