Wed March 04, 2015 By: Ravi Consul

Q.On a convex lens ,light of red and violet colour is incident separately , then how does the focal length of lens change?

Expert Reply
Yashvanti Jain
Thu March 05, 2015
If red light and violet is incident on a convex lens, you will observe that red lideviates the least and are brought to a focus at point R. Whereas, the violet rays are deviated the most and are brought to a focus at point V.
From the figure, we can see that the focal lenght of the lens for red colour light (OR) is more than that of violet (OV). Also, the focal lenght depends on the refractive index which depends on the wavelength.Hence, fr > fv
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