Tyndall Effect is the scattering of light by particles in its path like dust,water molecues etc
Explanation
We know that atmosphere is a mixture of several gases, dust particles, smoke, water particles etc
When sun light falls on the atmosphere,light particles get reflected from surface of these particles and get scattered in different directions
This is called Tyndall Effect
Examples of Tyndall Effect
Example 1
When a small ray of sunlight enters a dark room
We are able to see dust particles in the air
This is due to Tyndall Effect
It is because rays of sunlight are reflected off the surface of these dust particles and move in different directions
Example 2
In a dense forest, sunlight is not able to reach down because of shadow of number of trees
If some light is able to pass down from canopy of forest (upper layer of leaves of forest),we see scattering of light
This is because sunlight gets scattered off the water particles in the air
Activity to show Scattering of Light
Equipment Required
We take a Source of Light S
We take a water tank T and fill it with water
We take one Lens L1 and place it between S and T
On the other side of tank, we place a cardboard containing whole at center
We take another lens and place it on right of cardboard hole
We place a screen on the other side of lens
Procedure
When we switch on source of light,
Light Rays first fall on lens, then water tank, then from cardboard enter the other lens and finally hit the screen
We see that there is no scattering of light currently
Now, we dissolve 200 gm of hypo (sodium thiosulphate) and 1-2 ml of concentrated sulphuric acid into tank
We see the suphur particles forming in the tank
Now light rays reflect form this suphur particles
So 3 side of tank becomes blue
The right side first appears orange red color and then bright red color
Red colored image is formed on screen
Summary
Hence we can say that forming of red light on screen is because of tyndall effect
It is due to reflection of light rays on striking the suphur particles
Since most of blue color gets scattered, red color light rays ultimately reach the screen
