Start free

Physics · Geometrical Optics

JEE Main 2025 — 28 January, Evening Shift — Question 57

A concave mirror produces an image of an object such that the distance between the object and image is 20 cm . If the magnification of the image is ' -3 ', then the magnitude of the radius of curvature of the mirror is :

  1. Option A:

    3.75cm

  2. Option B:

    3.0cm

  3. Option C:

    7.5cm

  4. Option D:

    15cm

    Correct

Answer: D

Step-by-step solution

m=−3=−vu\mathrm{m}=-3=-\frac{\mathrm{v}}{\mathrm{u}} and v−u=20 cm\mathrm{v}-\mathrm{u}=20 \mathrm{~cm}

f=vuv+u=(−30)(−10)−30−10\mathrm{f}=\frac{\mathrm{vu}}{\mathrm{v}+\mathrm{u}}=\frac{(-30)(-10)}{-30-10}

∴R=+15\therefore \mathrm{R}=+15

images

Solution figure

Answer key and solution verified before publishing.

Practise Geometrical Optics

Start with this question, then two more from the same chapter — with a tutor that explains every step. Free.

Solve a similar one free
Exam
JEE Main 2025
Paper
28 January, Evening Shift
Subject
Physics
Chapter
Geometrical Optics
Topic
Reflection of Light at Curved Surfaces and Spherical Mirrors

More Geometrical Optics questions from this paper

A concave mirror produces an image of an object such that the… | JEE Main 2025 PYQ with Solution · DhiX AI