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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
- When a mass M is attached to the spring of force constant k,
- A beam of light contains two wavelengths 6500Å and 5200Å.
- If doubly ionised lithium atom is hydrogen like with atomic number 3, the wavelength
- If the angle of minimum deviation is 60° for an equilateral prism, then the refractive
- If the momentum of electron is changed by P, then the de-Broglie wavelength
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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