Why does a liquid rise in the dropper when we release the bulb?

Hi Aryan!

 

When we press and release the bulb of the dropper, the air inside it is removed. So the pressure inside the dropper decreases and becomes less than atmospheric pressure. When the bulb is released below liquid surface, atmospheric pressure pushes liquid inside until the pressure exerted by liquid column inside dropper becomes equal to that of atmosphere and due to this, the water enters into the dropper.

 

Cheers!!