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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
- If the nucleus ²⁷₁₃Al has nuclear radius of about 3.6 fm
- In the half wave rectifier circuit operating from 50 Hz mains frequency,
- Which gate can be obtained by shorting both the input terminals of a NOR gate?
- In an AC circuit the potential differences across an inductance and resistance joined
- If r be the distance of a point on the axis of a magnetic dipole from its centre
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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