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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
- Three particles A,B and C are thrown from the top of a tower with the same speed.
- If seperation between screen and source is increased by 2%. What would be the effect
- Rate of photoelectric emission is proportional to
- A 1 µA beam of protons with a cross-sectional area of 0.5 sq.mm is moving with a velocity
- A coil of resistance and 1.0 H inductance is connected to an a.c. source of frequency
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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