Optics 7 Question 12
12. A biconvex lens of focal length is in front of a plane mirror. The distance between the lens and the mirror is . A small object is kept at a distance of from the lens. The final image is
(2010)
(a) virtual and at a distance of
(b) real and at a distance of
(c) virtual and at a distance of
(d) real and at a distance of
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Solution:
- Object is placed at distance
from the lens. So first image will be formed at distance on other side. This image will behave like a virtual object for mirror. The second image will be formed at distance in front of the mirror, or at distance to the left hand side of the lens.
Now applying lens formula
Therefore, the final image is at distance
This is because ray of light is travelling from right to left.