Name: Eye: Structure and Parts
Uploaded: 2019-07-19
Duration: 5 min 36 s
Description: Do you know that eye is a powerful optical instrument or a camera? But it works using living cells. How does it process light energy? Curious! Don't wait, Get in!

Question

Draw a raw diagram of scattering of light in colloidal solution.

Accepted Answer

Scattering is the phenomenon of change in the direction of light on striking an atom, a molecule, a water droplet or a dust particle etc. The following diagram indicates an experimental setup to observe the scattering of light in a colloidal solution.

In this experiment, first, we have to place a strong source $(S)$ of white light at the focus of a converging lens $(L_{1})$ . This lens provides a parallel beam of light. Then, we have to allow the light beam to pass through a transparent glass tank $(G)$ containing clear water. Then allow the beam of light to pass through a circular hole $(H)$ made in a cardboard. Then, we have to obtain a sharp image of the circular hole on a screen $(X Y)$ using a second converging lens $(L_{2})$ , as shown in the above figure. Then, we have to dissolve about $200 g$ of sodium thiosulphate (hypo) in about $2$ litre of clean water taken in the tank. Next, we have to add about $1$ to $2 ml$ of concentrated sulphuric acid to the water.

We can see that fine microscopic sulphur particles precipitating in about $2$ to $3$ minutes. We can also observe that the blue light is formed from the three sides of the glass tank. The colour of the transmitted light from the fourth side of the glass tank facing the circular hole is first orange-red and then bright crimson red. The blue light from the three sides of the glass tank is due to the scattering of short wavelengths by minute colloidal sulphur particles. The colour obtained on the screen from the fourth side of the glass tank facing the circular hole is red because mainly the red colour of the white light beam reaches the screen after passing the colloidal sulphur solution in the glass tank as the blue colour is scattered and hence eliminated on the way.

Draw a raw diagram of scattering of light in colloidal solution.

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