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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
- The refracting angle of a prism is A and refractive index of the material of the prism
- If the half-life of a material is 10 yr, then in what time, it becomes 1/4th part
- The acceleration due to gravity near the surface of a planet of radius R and density d
- A dip needle vibrates in a vertical plane perpendicular to magnetic meridian. The time
- The parallel beams of monochromatic light of wavelength 4.5 x10⁻⁷ m passes through
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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