Question

In a spectrum of white light by a prism, the colour at the extreme end opposite the base of the prism is
A.)Violet
B.)Yellow
C.)Red
D.)Blue

Answer 1

Hint: Bending of light in a prism depends on the wavelength of the incident light. Smaller the wavelength, greater is bending on that particular colour and closer is that colour to the base of the prism.

Detailed step by step solution:
White light comprises of all colours of the VIBGYOR i.e. Violet, Indigo, Blue, Green, Yellow, Orange, Red. When we optically combine these colors we get white light. The wavelength of light defines the colour of the light and in VIBGYOR, wavelength increases from left to right. That means, Violet colour has minimum wavelength while Red colour has maximum wavelength. This is something that we need to keep in mind while solving questions like these.

Now prism is a triangular slab of transparent glass through which light can pass.

But before going into prism we must remember that when light passes from one medium to another, it undergoes refraction.

Refraction is the phenomena of bending of light when it travels from one medium to another. Now the amount of bending of light depends on the wavelength of light. Smaller the wavelength of light, greater is its bending when it passes from one medium to another. That is, we can say that the amount of bending of light is inversely proportional to wavelength of light.

This property of light leads to splitting of different colours of light when passes through a prism as shown in the figure. Violet bends the most because it has shorter wavelength compared to other colours and red colour bends the least and can be seen at the extreme end opposite to the base of prism.

Hence the correct answer to our question is option C.

Note: When light goes from rarer medium to denser medium(e.g. From air to glass), it bends towards the normal at the point of incidence when light travels from denser medium to rarer medium(e.g. From glass to air), it bends away from the normal at the point of incidence.