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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
- Consider two nuclei of the same radioactive nuclide. One of the nuclei was created
- An open pipe resonates with a tuning fork of frequency 500 Hz. It is observed
- The primary and secondary coil of the transformer have 50 and 1500 turns respectively
- The magnetic flux linked with a circuit of resistance 100Ω increases from 10 to 60 Wb.
- An inclined plane makes an angle of 30° with the horizontal.A solid sphere
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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