Q17 of 20 Page 72

Why is the ceiling and wall behind the stage of good conference halls or concert halls made curved?

The ceilings of concert halls, conference halls and cinema halls are curved so that sound after reflection reaches all corners of the hall. Sometimes a curved soundboard may be placed behind the stage so that the sound, after reflecting from the sound board, spreads evenly across the width of the hall.


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15

Sound produced by a thunderstorm is heard 10 s after the lightning is seen. Calculate the approximate distance of the thunder cloud. (Given speed of sound = 340 m s-1)

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For hearing the loudest ticking sound heard by the ear, find the angle x in the Fig.12.4.

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Represent graphically by two separate diagrams in each case

(i) Two sound waves having the same amplitude but different frequencies?


(ii) Two sound waves having the same frequency but different amplitudes.


(iii) Two sound waves having different amplitudes and also different wavelengths.

 19

Establish the relationship between speed of sound, its wavelength and frequency. If velocity of sound in air is 340 m s-1, calculate

(i) Wavelength when frequency is 256 Hz.


(ii) Frequency when wavelength is 0.85 m.