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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 rectangular coil of length 0.12 m and width 0.1 m having 50 turns of wire
- A particle has initial velocity(3i⃗ +4j⃗)and has acceleration (0.4i⃗ +0.3j⃗)
- If the density of earth is doubled keeping its radius constant then acceleration
- A person holding a rifle (mass of person and rifle together is 100 kg) stands on a smooth
- If two vectors 2i+3j+k and -4i-6j-λk are parallel to each other, then the value of λ is
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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