Question

How does the focal length of convex lens changes with increase in wavelength of incident light?

Answer 1

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inversely with refractive index, its also varies inversely with the wavelength .

Focal length increases with wavelength and decreases with refractive index .

As we all know that Cuachy's equation gives relationship between refractive

index and wavelength of light for a particular transparent material and again  

lens formula gives a relationship between focal length and refractive index, so  

eliminating refractive index term from both equation should give you a  

mathematical relation between the wavelength and the focal distance.

n(λ) = B + C/λ²

Here B and C are coefficient determined for the material .

Hope it helps

Answer 2

Answer:

The focal length of a convex lens increases as the wavelength increases. This is so because the refractive index decreases with an increase in wavelength of light.