Question

you're given three lenses of power +5D,+1D.how will you combine to get a focal length a)+50 cm b)-50 cm

Answer 1

Answer:

Assuming the two lenses are in contact we have 1/f = 1/f1 + 1/f2

where the total power 1/f = power = 5D

We know, P = 1 / f (that is, 1D) where f = 1 m. The units of dioptre is 1/m .

Therefore, 100/15 + 1/f2 = 5

1/f2 = -25/15

f2 = -15/25

= -0.6 = -60 cm.

Hence, the focal length of B is -60 cm.

Answer 2

-60cm...

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