Question

What do you observe when
(a) Ice cold water is filled in a glass tumbler.
(b) A beam of light is allowed to enter a closed dark room through a small hole.

Answer 1

(a) Condensation is the process in which water vapour becomes liquid at specific conditions. It is the opposite of evaporation, where liquid becomes a vapour.
(b) Tyndall effect is the scattering of a beam of light by any medium containing small suspended particles like smoke or dust in a room, which makes a light beam entering a window clearly visible.

Complete answer:
(a) We will observe that fine water droplets are getting deposited on the outer wall of the glass tumbler when ice cold water is filled in it. On a typical humid day, a bottle of cold water will cool the air around the bottle causing the air to saturate. Once the air around the bottle gets saturated to its maximum, the excess water vapour will condense out as liquid droplets on the surface of the bottle.
(b) When a beam of light is allowed to enter a closed dark room through a small hole we will observe randomly moving dust particles in the beam of light. This will confirm the presence of dust particles in the air. This effect is known as the Tyndall effect.

Note:
-Tyndall effect can also be observed when sunlight passes through the tiny holes made by leaves in the canopy of a dense forest. The Tyndall effect is also responsible for the scattering of car light in the fog.
-Condensation is the cause for the morning dew on the grass, clouds in the sky, Fog in the air and fogging of mirrors.