Question

How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light? Draw the diagram.

Answer 1

Prism

1. Prism is a transparent medium, that deflected light rays.
2. In prism, the velocity is different for light rays of different frequencies (monochromatic light rays).
3. For two identical prisms, the angle of deflection is the same.

Deflection of light rays in two mutually inverted prisms

1. We know in the case of two identical prisms, the angle of deflection is the same. If two prisms are inverted with each other then the white light rays incident on the first prism will be deflected.
2. And the deflected light rays again deflect by the second inverted prism in equal amounts.
3. We know that the deflection angle of light is the same in a prism for a particular incident angle. The two opposite deflections of the same incident angle will cancel out, as shown in the figure. So the net deflection is zero.
4. A narrow beam of white light incident on mutually inverted prisms will emerge out of white lights.
5. In this phenomenon, white light is first dispersed into its seven constituent colors. When this dispersed light is incident on the second prison again, they recombine into white light.

Diagram