    Question

# The real image of an object placed on the principal axis of a concave mirror of focal length 12 cm is formed at a point which is 10 cm more distant from the mirror than the object. The magnitude of magnification of the image is:

A
2.0
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B
1.5
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C
0.67
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D
2.5
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Solution

## The correct option is B 1.5Since the mirror is concave, focal length is f=−12 cm Let u be the object distance and v be image distance. Using mirror formula, 1u+1v=1−12⋯(i) Given, image is 10 cm more left than the object. Image distance is: v=u−10⋯(ii) Substituting (ii) in (i), we get: 1u+1u−10=1−12 u−10+u(u−10)u=1−12 Simplifying, we get u2+14u−120=0 u={−20 cm, 6 cm} Object distance cannot be positive. u=−20 cm Image distance is: v=u−10=−30 cm Magnification is given by: m=−vu m=−(−30)−20 m=−1.5 Magnitude of magnification is: |m|=1.5  Suggest Corrections  0      Similar questions  Explore more