Question

A convex glass lens is immersed in water. Compared to the power in air, its power in water will :

A

increase

B

decrease

C

not change

D

decrease for red light and increase for violet light

Easy

Solution

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Correct option is B)

Power of a lens

Where is the focal length of the lens.

So, by lens maker formula


As lens is dipped in water, of the medium is increased from 1 to (i.e. refractive index of water), so, term decreases, so, term decrease which leads to decrease of so, power  decreases.

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