Question

The focal length of a convex lens made of flint glass is . To remove its chromatic aberration, it is placed in contact with a concave lens made of crown glass. Find the focal length of the concave lens. The ratio of dispersive powers of flint glass to crown glass is .

A

B

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D

Medium
Updated on : 2022-09-05
Solution
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Correct option is A)

Given: The focal length of a convex lens made of flint glass is 15cm. To remove its chromatic aberration, it is placed in contact with a concave lens made of crown glass. The ratio of dispersive powers of flint glass to crown glass is 1.5.
To find the focal length of the concave lens
Solution:
Let focal length of the convex lens be and focal length of the concave lens be and ratio of dispersice power of the flint glass is $$\dfrac {\omega_2}{\omega_1}=1.5$$
For achromatic combination,
Hence the focal length of the concave lens is -10cm

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