Question

Does focal length depend upon a colour of light ? explain with red and violet light.

Answer 1

Remember focal length is the property of lens and colour of light is dependent of wavelength. So focal length of the lens is independent of the colour, wave length and frequency of the light which is passing through the lens.
Note: Refraction of light is colour dependent. The light with more wavelengths like red refracts the least and the colour with minimum like violet wavelength refracts the maximum.

Answer 2

Answer:

The refractive index of the material of a lens increases with the decrease in wavelength of the incident light. ... Thus, when we replace red light with a violet wavelength decrease and hence the focal length of the lens also decrease