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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
- A particle moves from position r₁ = 3i + 2j -6k to position r₂ = 14i + 13 j+ 9 k
- In a Rutherford scattering experiment when a projectile of charge Z₁ and mass M₁
- Photoelectric emision occurs only when the incident light has more than a certain minimum
- A uniform rod of length l is placed with one end in contact with the horizontal
- The wavelength λₑ of an electron and λₚ of a photon are of same energy E are related by
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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