Question

the power of combination of two lenses X and Y is 4D. If the focal length of X is 12 CM calculate the focal length of Y and nature of lens Y

Answer 1

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Answer 2

The Len Y is a concave lens and the focal length is -22 cm

GIVEN

the power of combination of two lenses X and Y is 4D. If the focal length of X is 12 cm

TO FIND

The focal length of Y and nature of lens Y

SOLUTION

The above problem can be simply solved as follows;

Power = 1/Focal length

Power of X = 1/0.12 = 100/12 = 8.3D

Power of Y = -4.4 D

Power of Y lens = -(1/F)

-4.4 = 1/F

F = -1/4.4

= -0.22 m = -22 cm

Since, The focal length is negative the lens is concave.

Hence, The Len Y is a concave lens and the focal length is -22 cm

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