Q.10 When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to
(a) pressure of water
(b) gravity of the earth
(c) shape of rubber bulb
(d) atmospheric pressure

Atmospheric pressure.

EXPLANATION

When we press the bulb of a dropper with its nozzle kept in water, air in the dropper escapes in the form of bubbles. As all the air is removed by pressing the bulb of dropper, so the pressure of air inside the bulb decreases. The atmospheric pressure outside the bulb of the dropper i.e., pressure of air in the water becomes higher than the inside pressure of the bulb. So the air in the water flows from high pressure region to low pressure region i.e., towards the inside of the bulb. As a result there is rise of water in the dropper.