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?

The answer is :  We’ll see the bell move, but we won’t hear it ring.  This is    because light can travel through vacuum but sound cannot.  Sound waves are vibrations of particles in any media, so sound requires a medium to travel, and it cannot travel in a vacuum as there is no particles to vibrate.