KVPY SA Exam 05-Nov-2017 Question Paper

Question : 24 of 80

Marks: +1, -0

A point source of light is placed at 2f from a converging lens of focal length f. A flat mirror is placed on the other side of the lens at a distanc d such that rays reflected from the mirror are parallel after passing through the lens again. If f = 30 cm, then d is equal to

15 cm.
30 cm.
45 cm.
75 cm.

Validate

Solution:

\at 2f – object then image will also be at ‘2f’. Finally image is at ∞ therefore after reflection from mirror. Image must be formed at focus.

d={\f+2\f}/2=45

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