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Question 45Asked in RRB JE CBT-1, 19 Feb 2026, Shift 1 (9:00 AM)

A physicist uses a convex lens to focus sunlight onto a piece of paper and notices the

A physicist uses a convex lens to focus sunlight onto a piece of paper and notices the smallest, brightest spot forms at a certain distance from the lens. Which property of the lens does this experiment help to determine?
  1. AThe experiment helps to determine the principal axis of the lens.
  2. BThe experiment helps to determine the optical center of the lens.
  3. CThe experiment helps to determine the diameter of the lens.
  4. DThe experiment helps to determine the focal length of the lens.
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Correct answer: (D) The experiment helps to determine the focal length of the lens.

From RRB JE CBT-1 PYQ 19 Feb 2026, Shift 1 (9:00 AM)

This is question 45 of RRB JE CBT-1 PYQ 19 Feb 2026, Shift 1 (9:00 AM). See all questions of this paper with answers, or attempt the paper as a timed online test to get your score and all-India rank.