Question

The power of two lenses are +12d and -2d. they are placed in contact on the same axes. what will be the focal length of the combination?

Answer 1

Answer:

The focal length of the combination is = 10 cm.

Explanation:

The focal length of the first lens = 1 / 12 m = 0.083333 m

The focal length of the second lens = - 1/2 m = 0.5 m

If ' f ' be the focal length of the combination then

1/f = ( 1/0.08333 ) - ( 1/ 0.5 )

= 10

So f = 1/10 m = 0.1 m = 10 cm

Answer 2

Answer:-

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