Why is Tyndall effect shown by colloidal particles? State four instances of observing the Tyndall effect.

OR

Differentiate between a glass slab and a glass prism. What happens when a narrow beam of (i) a monochromatic light, and (ii) white light passes through

(a) glass slab and

(b) glass priam?

The Tyndall effect is the phenomenon in which the particles in a colloid scatter the beams of light that are directed at them. This effect is exhibited by all colloidal solutions and some very fine suspensions as governed by the Rayleigh scattering.

The intensity of scattered light depends on the density of the colloidal particles as well as the frequency of the incident light.

Instances of tyndall effect: -

1. The visible beam of headlights in fog is caused by the Tyndall effect. The water droplets scatter the light, making the headlight beams visible.

2. Shining a flashlight beam into a glass of milk is an example of the Tyndall effect.

3. Sunlight entering in a room full of dust

OR

(a)

Glass slab:

(i) Monochromatic:

When a monochromatic beam of light passes through a glass slab, the light ray suffers a lateral displacement while the incident light ray is parallel to the emergent ray

(ii) White Light:

In case of white light also the beam of light will be deviated from its original path with a lateral displacement but the opposite sides are parallel and therefore different colors emerge parallel to each other and are seen simultaneously. Therefore, dispersion doesn't occur in a glass slab.

(b) Glass Prism :

(i) Monochromatic:

In the case of monochromatic light the ray will bend due to refraction but it will not show dispersion of light.

(ii) White Light:

When a white beam of light is allowed to pass through the prism, it will get dispersed into its 7 color component of spectrum of light. The splitting of light into its component colours is called dispersion.