Mon February 28, 2011 By: Aisha Khan

What is the radius of curvature of a spherical mirror whose focal length is – 0.5 cm? Also name the type of mirror. This ques. is from topper question bank. please answer that how is it possible to tell that the mirror is concave and not convex.

Expert Reply
Wed March 02, 2011
Dear student
Focal length f = R/2
So R = 2f= -1 cm.
Negative rdaius of curvature or focal length implies that the mirror is concave.
Cocave mirror has its focus point onto its left, as it converges the incident parallel rays. So the measure of its focal length from the pole of the mirror as per sign conventions will be negative.
Similarly for convex mirror , it produces virtual focus onto the right.So teh emasure of focal length from its pole will be positive.
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