A concave lens of focal length 20 cm product an image half in size of the real object. The distance of the real object is

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Question: Answered & Verified by Expert

A concave lens of focal length

20 cm

product an image half in size of the real object. The distance of the real object is

PhysicsRay OpticsNEET

Options:

A $20 cm$
B $30 cm$
C $10 cm$
D $60 cm$

Solution:

2787 Upvotes Verified Answer

The correct answer is:

20 cm

We know that

m = \frac{f}{f + u}

\frac{1}{2} = \frac{- 20}{- 20 + u} o r - 20 + u = - 40

Or

u = - 40 + 20

or

u = - 20 c m

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