In the following statements, tick ‘T’ against those which are true and ‘F’ against those which are false. (a) Sound cannot travel in a vacuum. (T/F) (b) The number of oscillations per second of a vibrating object is called its time period. (T/F) (c) If the amplitude of the vibration is large, the sound is feeble. (T/F) (d) For human ears, the audible range is 20 Hz to 20,000 Hz. (T/F) (e) The lower the frequency of vibration, the higher the pitch. (T/F) (f) Unwanted or unpleasant sound is termed as music. (T/F) (g) Noise pollution may cause partial hearing impairment. (T/F)

Soln:

1. a) True – A medium is required for sound to travel
2. b) False – A vibrating object whose number of oscillations per second is known as its frequency. The time taken to complete one oscillation is called a time period.
3. c) False – The square of the amplitude of vibration is proportional to the loudness of sound. Sound is loud when the amplitude of vibration is large. For a feeble sound, the amplitude is small.
4. d) True – Sounds of all frequencies are not audible to human ears. The range of frequencies which are audible to human ears is between 20 Hz and 20,000 Hz. Sounds outside these frequencies are not audible to human ears.
5. e) False – Higher the frequency, the higher the pitch of the sound, as the pitch is proportional to its frequency. For high-pitched sounds, its vibrating frequency is high, and for low-pitched sounds, its vibrating frequency is small.
6. f) False – Music is a melodious and pleasing sound which is pleasant to hear. Noises are unpleasant sounds.
7. g) True – Noises are unwanted and unpleasant sounds which cause temporary hearing impairment when heard continuously for a long period of time.