An eye-piece consists of a concave lens of focal length 2f and a convex lens of focal length 3f separted by a distance `(f)/(2)`. They are of the same

Monjur Alahi

An eye-piece consists of a concave lens of focal length 2f and a convex lens of focal length 3f separted by a distance `(f)/(2)`. They are of the same material. Examine whether the eye-piece formed is free from spherical and chromatic aberration. Is it suitable for use of cross-wire?
[Hint : An eye-piece is suitable for cross-wire when it is a positive one. See example 6]


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Correct Answer - Free from chromatic aberration but not spherical, yes

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