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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 primary of a transformer when connected to a dc battery of 10 volt draws a current
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Topics: Ray Optics
(94)
Subject: Physics
(2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- The primary of a transformer when connected to a dc battery of 10 volt draws a current
- A light of wavelength 5000Å falls on a sensitive plate with photoelectric work
- Minimum and maximum values of Poisson’s ratio for a metal lies between
- Light of wavelength 500 nm is incident on a metal with work function 2.28 eV.
- An object is seen through a simple microscope of focal length 12 cm.
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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