Optics 7 Question 17
17. A diminished image of an object is to be obtained on a screen $1.0 m$ from it. This can be achieved by placing
(a) a plane mirror
$(1995,2 M)$
(b) a convex mirror of suitable focal length
(c) a convex lens of focal length less than $0.25 m$
(d) a concave lens of suitable focal length
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Solution:
- Image can be formed on the screen if it is real. Real image of reduced size can be formed by a concave mirror or a convex lens.
A diminished real image is formed by a convex lens when the object is placed beyond $2 f$ and the image of such object is formed between $f$ and $2 f$ on other side. Thus, $d>(2 f+2 f)$ or $4 f<0.1 m$ or $f<0.25 m$
