(a) Why the stage of an auditorium has curved background, curtains, carpets and false ceiling? (b) The sound of a ringing bell inside a vacuum , chamber cannot be heard. Why?

CBSE Class 9 CBSE Class 9 Science
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(a) The curved surface is used to spread the sound in all directions. The curtains, carpets
and the false ceiling are used to prevent echo from occurring in the auditorium.
(b) This is because sound requires a medium to propagate.

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The answer to the following questions are:
(i)The stage of an auditorium has a curved background, curtains, carpets & false ceiling because it has the property to spread the sound throughout the whole area (auditorium) and it also prevents the formation of echo.
(ii)The sound of the ringing bell inside a vacuum couldn’t be heard because sound requires a medium to propagate(travel).