Explain the refraction of light with the help of a glass prism
Answers
A glass prism is a transparent object having two triangular ends and three rectangular sides. The refraction of light in glass prism is different from a glass slab. This is because in glass prism, the incident ray of light is not parallel to emergent ray of light.
Refraction of Light through a Glass Prism:
If you take a glass prism, you can see that it has 2 triangular bases and three rectangular lateral surfaces, inclined at an angle. This angle is called the angle of the prism.
Let’s look at a top view of a triangular prism with a ray of light entering it.
In the figure shown, A is the angle of the prism.
- As per Snell’s law, light traveling from a rarer medium to a denser medium bends towards the normal, and vice versa. Glass is denser than air, and thus, when a ray of light falls on the surface of the prism, it bends towards the normal. According to the diagram, ray PE falls on the surface of the prism and bends towards the normal NE.
- Then, while moving from the glass to air, the emergent ray FS bends away from the normal.
- ∠HDS is the angle of deviation which tells us how much the emergent ray has deviated from the incident ray. When the angle of incidence is equal to the angle of emergence, the angle of deviation is minimum.
- According to the figure, ∠PEN = ∠MES and ∠HDS is thus the angle of minimum deviation. The refracted ray EF is parallel to side BC in this case.
This is how a ray of white light scatters into 7 colours when it passes through a prism. The different colors of light wave experience a different degree of deviation and thus white light splits into its components when it is subjected to refraction.
