Question

Two thin convex lenses of focal length 20 cm and 25cm are placed in closed contact with a concave lens of focal length 40 cm. The effective power of the combination is​

Answer 1

Answer:

20cm

Explanation:

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Answer 2

Given:

convex lenses of focal length 20 cm and 25 cm are placed concave lens of focal length 40 cm.

To find:

The effective power of the combination

Explanation:

$P_{1} =\frac{100}{20}=5D$

$P_{2} =\frac{100}{25} =4D$

Effective power $P=P_{1} +P_{2}$

=5+4

=9D

Answer:

The effective power of the combination in 9D.