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An object placed at 20 cm in front of a concave mirror produces three times magnified real image. What is the focal length of the concave mirror?
Options
(a) 15 cm
(b) 6.6 cm
(c) 10 cm
(d) 7.5 cm
Correct Answer:
15 cm
Explanation:
We know that, linear magnification, m = f / (f -u) —-(i)
Given, object displaced, u = -20 cm
m = -3 (All real images are inverted)
Substituting the above values in equation (i), we get
-3 = f / [f – (-20)]
⇒ -3f – 60 = f 4f = -60
⇒ f = – 60 / 4 = -15 cm
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Topics: Ray Optics
(94)
Subject: Physics
(2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- The acceleration due to gravity becomes (g/2) where g=acceleration due to gravity
- The de-Broglie wavelength of an electron in the first Bohr orbit is
- The surface tension of a liquid is 5 newton per metre. If a film
- The phase difference between the instantaneous velocity and acceleration of a particle
- The fundamental frequency of a closed organ pipe of length 20 cm is equal to the second
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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