JEE Main · 2024 · 04 Apr 2024 · Shift 1 · Geometrical Optics

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An effective power of a combination of 5 identical convex lenses which are kept in contact along the principal axis is 25 D . Focal length of each of the convex lens is :

(A)20 cm✓ Correct
(B)50 cm
(C)500 cm
(D)25 cm

Answer: (A)

Solution

For lenses in contact the powers add:

P_{eq} = \sum P_{i} = 5 P = 25 D \Rightarrow P = 5 D .

Focal length of each lens:

f = \frac{1}{P} = \frac{1}{5} m = 0.2 m = 20 cm .

Option A.

JEE Main · 2024 · 04 Apr 2024 · Shift 1 · Single correct option

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