Class 12 Physics Chapter 9: Ray Optics and Optical Instruments Assertion-reason questions with answers
2 assertion-reason questions on Ray Optics and Optical Instruments, each with its answer and the reason, written from the NCERT chapter. For the CBSE board, JEE Main and NEET, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter. Each question gives an Assertion (A) and a Reason (R); choose how they stand to each other.
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Answer: (a) Both A and R are true, and R is the correct explanation of A.
In air (n₂/n₁ − 1) = 0.5 > 0 and the convex shape gives f > 0. In the liquid, 1.5/1.7 − 1 < 0 while (1/R₁ − 1/R₂) is still positive, so f < 0: the lens diverges. R is the relation that makes A true.
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Answer: (b) Both A and R are true, but R is not the correct explanation of A.
Both statements are true. A mirror forms images by reflection, which does not depend on wavelength, so it has no chromatic aberration. Support over the back surface is a separate advantage, about weight and mechanical strength; it does not explain the absence of chromatic aberration.