Sound — Set 1
Physics · ध्वनि · Questions 1–10 of 60
Which statement about sound propagation is correct?
Correct Answer: A. Sound cannot travel through a vacuum.
Sound needs a material medium to transmit vibrations. In a vacuum there are no particles to vibrate and carry the wave. That is why space is essentially silent for sound.
What is the SI unit of frequency?
Correct Answer: C. Hertz
Frequency counts how many oscillations occur each second. The SI unit for per second is hertz or Hz. A higher frequency generally corresponds to a higher perceived pitch.
For sounds of the same frequency, which factor mainly decides loudness?
Correct Answer: A. Amplitude of vibration
Loudness is mainly linked to the amplitude of the sound wave. Larger amplitude carries more energy and usually sounds louder. Intensity in simple cases increases with the square of amplitude.
Beats are commonly produced when two sound waves have?
Correct Answer: A. Slightly different frequencies
Beats occur due to interference of two close frequencies. The loudness rises and falls as the waves alternately reinforce and cancel. This effect is used when tuning musical instruments.
A change in the observed pitch due to relative motion between source and listener is called?
Correct Answer: A. Doppler effect
The Doppler effect changes the observed frequency when source and observer move relative to each other. Approaching motion generally increases the observed pitch. It is commonly noticed with passing sirens.
In gases, the speed of sound generally increases when?
Correct Answer: C. Temperature increases
In a gas, higher temperature means faster moving molecules. Faster molecular motion allows disturbances to pass along more quickly. So the speed of sound in air rises as temperature rises.
In general, sound travels fastest in?
Correct Answer: A. Solids
Sound speed depends strongly on how tightly particles are connected. Solids usually have much greater stiffness, so vibrations pass rapidly through them. That is why you can hear a train through a rail earlier than through air.
An echo is produced mainly due to?
Correct Answer: A. Reflection of sound
An echo happens when sound reflects from a distant surface. The reflected wave returns to the listener after a delay. Hard, large surfaces like cliffs can produce clear echoes.
Resonance occurs when the driving frequency is?
Correct Answer: B. Equal to the natural frequency of the system
Resonance happens when an external periodic force matches a system's natural frequency. Energy transfer becomes very efficient and the amplitude can grow large. This is why pushing a swing at the right rhythm makes it go higher.
The quality or timbre of a musical sound mainly depends on?
Correct Answer: A. Its waveform and overtones
The correct answer is 'Its waveform and overtones'. Timbre is determined by the mixture of harmonics and the shape of the wave. Different instruments produce different overtone patterns even for the same note. This is why a flute and a violin sound different at the same pitch.