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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
Related Questions: - Two conducting spheres of radii 5 cm and 10 cm are given a charge of 15 μC each.
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Topics: Ray Optics
(94)
Subject: Physics
(2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- Two conducting spheres of radii 5 cm and 10 cm are given a charge of 15 μC each.
- The threshold frequency for a certain photosensitive metal is ν₀. When it is illuminated
- The electric field at a distance 3R / 2 from the centre of a charged conducting
- A cricket ball of mass 250 g collides with a bat with velocity 10 m/s
- An amplifier has a voltage gain Av=1000. The voltage gain in dB is
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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