Physics · Geometrical Optics

JEE Main 2026 — 22 January, Evening Shift — Question 31

In parallax method for the determination of focal length of a concave mirror, the object should always be placed :

Option A:
between the focus (F) and the centre of curvature (C) of the mirror ONLY
Option B:
at any point beyond the focus $(\mathrm{F})$ of the mirror
Correct
Option C:
beyond the centre of the curvature ( C ) of the mirror ONLY
Option D:
between the pole ( P ) and the focus ( F ) of the concave mirror ONLY

Answer: B

Step-by-step solution

Image should be real. So object should be placed beyond focus.

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 22 January, Evening Shift
Subject: Physics
Chapter: Geometrical Optics
Topic: Experiments for Determination of Focal Length of Lens & Mirrors

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In parallax method for the determination of focal length of a concave… | JEE Main 2026 PYQ with Solution · DhiX AI