Failed to connect to MySQL: Access denied for user 'examnext_online'@'localhost' (using password: YES) A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is `3/2`. Their equivalent focal length is 30 cm. What are their individual focal length? - Sarthaks eConnect

A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is `3/2`. Their equivalent focal length is 30 cm. What are their individual focal length?

A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is `3/2`. Their equivalent focal length is 30 cm. What are their individual focal length?

A.

-75, 50

B.

-10, 15

C.

75, 50

D.

-15, 10

Solution

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Best answer

Let focal length of convex lens is +f, then focal length of concave lens would be `-3/2f`

From the given condition,

`1/30=1/f-2/(3f)=1/(3f)`

so, f=10 cm

Therefore, focal length of convex lens=+10 cm and that of concave lens =-15 cm