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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: - The radioactivity of a certain material drops to 1/16 of the initial value in 2 hours.
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Topics: Ray Optics
(94)
Subject: Physics
(2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- The radioactivity of a certain material drops to 1/16 of the initial value in 2 hours.
- When photons of energy hν are incident on the surface of photosensitive
- Moment of inertia, along the diameter of a ring is
- Zenor breakdown will occur if
- A fluid is in streamline flow across a horizontal pipe of variable area of cross section
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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