An image of small size can be obtained on a screen placed at 2.0 m from object. It can be done
by using.
(A) concave mirror of focal length 0.5 m
(B) concave mirror of focal length greater than 0.5 m
(C) concave mirror of focal length less than 0.5 m
(D) concave lens of focal length less than 0.5 m.

2

Answers

2015-07-19T17:46:00+05:30
A real image is obtained only in case of concave mirror or convex lens.
So option (D) is out.

Rest choices involve concave mirror only. So i will analyse for concave mirror only(exclude convex lens)

Object is placed at -2.0m.
Since image is small, diminished image is formed.
For concave mirror, 
- a diminished image is formed when object is beyond 2F
(Rest cases are:
- a point image is formed when object is at infinity(not the case here)
- a enlarged image is formed when object is between F and 2F.(not the case)
- a image of same size is formed when object is at 2F (not the case))

So 2m is beyond 2F. That means F is less than (2/2)m or 1m.
So option A and C are correct.

Option B is not fully correct as greater than 0.5 doesn't mean less than 1m. So only answers are A and C.

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  • Brainly User
2015-07-19T17:53:43+05:30
It can be done by using;- (C) concave mirror of focal length less than 0.5 m
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