Question

An electric bell is kept under a bell jar in which a vacuum has been created. slowly air is introduced in to the jar. what will happen to the sound of the electric bell? a. it will increase until it reaches its maximum. b. it will decrease until it stops. c. it will not change. d. it will increase and decrease periodically. e. it will decrease exponentially.

Answer 1

a) it will increase until it reaches its maximum

Sound requires a medium (air in this case) in order to propagate because it is a "compressional" wave as opposed to light which is a "transverse" wave and does not need a medium present for propagation.