Question

What is the dispersion of light? State its cause and draw a ray diagram to show the dispersion of white light by a glass prism.

Answer 1

Hint: The concept of the refraction is responsible for the dispersion of the light. The white light is not monochromatic as we generally understand. The white light is composed of different wavelengths and hence different frequencies and therefore we can see different refraction angles of the light.

Complete step by step solution:
The white light is a combination of the different wavelengths and here when the light passes through the denser media we are able to see the components or the different wavelengths present in the white light.

Let us first understand what is refraction.
We know that when the light goes from the denser to the rarer media the light bends and this bending of the light is called the refraction of the light.

The angle of the bending or the refraction is dependent on the value of the density of the media and also the wavelength of the light passing through the denser media.
Higher the wavelength lesser the bending angle and hence now we can explain the process of the diffraction using the above concepts.

In the above diagram we can see that when the white light is incident on the prism we are getting the light with different colors which represent different wavelengths. As the prism is a denser body we are seeing that different wavelengths are bending at different angles and we are able to see different wavelengths

The white composed of the many wavelengths when passes through the denser media the wavelengths present in the white light bend at different angles depending on the wavelengths and here the wavelengths having the maximum value bend the least and the wavelength s having the max value bend the most.

Now we have seen that due to the different wavelengths present in the white light we can see the different wavelengths present in the white light. As some of the wavelengths present in the white light are in the visible spectrum we are able to see them with our eyes.

Thus the dispersion phenomenon occurs in nature.


Note: There is one common misconception that the colors which we see are the only wavelengths present in the white light which is wrong and here we need to comprehend that the white light consists of many wavelengths and they also bend at different angles through the prism, but we cannot see them as most of them are not in the visible spectrum.