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A person wants a real image of his own, 3 times enlarged. Where should he stand in front of a concave mirror of radius of curvature of 30 cm?
Options
(a) 90 cm
(b) 10 cm
(c) 20 cm
(d) 30 cm
Correct Answer:
20 cm
Explanation:
Given, m = -3 and R = 30 cm
f = -(R / 2) = -15 cm
We know that, m = -(v / u) ⇒ -3 = -v / u
Therefore, v= 3u
1/f = (1/v) + (1/u) ⇒ (1/-15) = (1/3u) + (1/u) = (1+3) / 3u
-3u = 4 × 15
u = (-4 × 15) / 3
Initial position of a person, u = -20 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 bullet loses 1/20 of its velocity after penetrating a plank.How many planks
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- Two identical cells of the same e.m.f. and same internal resistance
- A satellite A of mass m is at a distance r from the centre of earth. Another satellite
- A microscope is having objective of focal length 1 cm and eye-piece of focal length 6 cm.
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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