Distance between virtual image, which is twice the size of object placed in front of mirror and object is 45 cm. The magnitude of focal length of the mirror is _____cm.
Solution and Explanation
The Correct Answer is : 30
\(|m|=|\frac{v}{u}|=2\)
\(|v|=|2u|\)
n + 2n = 45
n = 15 cm
u = –15
v = 30
\(\frac{1}{v}+\frac{1}{u}=\frac{1}{f}\)
\(\frac{1}{30}+\frac{1}{-15}=\frac{1}{f}\)
\(\frac{1-2}{30}=\frac{-1}{30}=\frac{1}{f}\)
\(⇒ f=30\ cm\)
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Concepts Used:
Spherical Mirrors
A spherical mirror is a mirror which has been cut out of a spherical surface.
There are two kinds of spherical mirrors:
- Convex Mirror
- Concave Mirror
Concave Mirror
Concave mirrors are also called converging mirrors, because in these types of mirrors, light rays converge at a point after impact and reflect back from the reflective surface of the mirror.
Convex Mirror
The convex mirror has a reflective surface that is curved outward. Regardless of the distance between the subject and the mirrors, these mirrors are "always" virtual, upright and reduced.