Question

An electric bell is placed inside a transparent glass jar. The bell can be turned on and off using a switch on the outside of the jar. A vacuum is created inside the jar by sucking out the air. Then the bell is rung using the switch. What will we see and hear?

Answer 1

We can see the bell ringing but can't hear it.

Because the law of sound says that sound needs a medium to propagate

Answer 2

First of all perfect vacuum can't be created anywhere on earth so the sound that the bell will produce will be less than 20hz so we can't here the bell ringing hence we will not here the bell ringing.
Hope helped