Verified Solution • 2025–26 Session moderate

QJEEM22Phb08c: JEE Main 2022 Physics - Class 12 JEEM22Phb08c Solution: A convex lens of focal length 20 cm is placed in front of a…

A convex lens of focal length 20 cm is placed in front of a convex mirror with principal axis coinciding each other. The distance between the lens and mirror is 10 cm. A point object is placed on principal axis at a distance of 60 cm from the convex lens. The image formed by combination coincides the object itself. The focal length of the convex mirror is ____________ cm.

Step-by-Step Verified Solution

JEE Main 2022 (Online) 25th July Evening Shift Physics - Geometrical Optics Question 89 English Explanation

1v+1u=1f{1 \over v} + {1 \over u} = {1 \over f}

1v−1−60=120{1 \over v} - {1 \over { - 60}} = {1 \over {20}}

1v=−160+120=−1+360=260{1 \over v} = - {1 \over {60}} + {1 \over {20}} = {{ - 1 + 3} \over {60}} = {2 \over {60}}

⇒v= + 30\Rightarrow v = \, +\, 30 cm

∴\therefore Radius of curvature of mirror = 30 −- 10 = 20 cm

⇒fmirror=202=10\Rightarrow {f_{mirror}} = {{20} \over 2} = 10 cm

Related Learning Resources & Exam Preparation

JEE Main PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring