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Q.3 In the following statements, tick ‘T’ against those which are true, and ‘F’ against those which are false. (a) Sound cannot travel in 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 vibration is large, 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 is 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)

(a) Sound cannot travel in vacuum. ( T )

(b) The number of oscillations per second of a vibrating object is called its time period. ( F )

(c) If the amplitude of vibration is large, sound is feeble. ( F )

(d) For human ears, the audible range is 20 Hz to 20,000 Hz. ( T )

(e) The lower the frequency of vibration, the higher is the pitch. ( F )

(f) Unwanted or unpleasant sound is termed as music. ( F )

(g) Noise pollution may cause partial hearing impairment. ( T )

EXPLANATION

Sound waves travel from one point to another through vibrations of particles in the medium. As vacuum doesn't have any medium, so there are no atoms or molecules to vibrate and thus sound doesn't travel in vacuum.

The number of oscillations per second of a vibrating object is called as frequency and time period is the time taken by the vibrating object to complete one oscillation.

If the amplitude of vibration is large, then the sound is very strong and large. And when the amplitude of vibration is small, then the sound is feeble.

For human ears, the audible range is 20 Hz to 20,000 Hz. The sound below 20 Hz is called as infrasonic sound and the sound above 20,000 Hz is called as ultrasonic sound. Both infrasonic sound and ultrasonic sound is not audible to human ears.

The lower the frequency of vibration, the lower is the pitch and the higher the frequency of vibration, the higher is the pitch.

Unwanted or unpleasant sound is termed as noise while the pleasant and soothing sound is considered as music.

Noise pollution may cause partial hearing impairment and also many mental health problems.