| ⇦ | 
| ⇨ |
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: - If r be the distance of a point on the axis of a magnetic dipole from its centre
- The number of beta particles emitted by a radioactive substance is twice the number
- The periodic waves of intensities I₁ and I₂ pass through a region at the same time
- A body travelling along a straight line traversed one-third of the total distance
- When the energy of the incident radiation is increased by 20%,
Topics: Ray Optics
(94)
Subject: Physics
(2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- If r be the distance of a point on the axis of a magnetic dipole from its centre
- The number of beta particles emitted by a radioactive substance is twice the number
- The periodic waves of intensities I₁ and I₂ pass through a region at the same time
- A body travelling along a straight line traversed one-third of the total distance
- When the energy of the incident radiation is increased by 20%,
Topics: Ray Optics (94)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
18000+ students are using NEETLab to improve their score. What about you?
Solve Previous Year MCQs, Mock Tests, Topicwise Practice Tests, Identify Weak Topics, Formula Flash cards and much more is available in NEETLab Android App to improve your NEET score.
Share this page with your friends
Leave a Reply