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Science — CBSE Class 10 board question

Q1. [1]
Assertion (A) : Red light signals are used to stop the vehicles on the road. Reason (R) : Red coloured light is scattered the most so as to be visible from a large distance.
  1. A Both (A) and (R) are true and (R) is the correct explanation of (A).
  2. B Both (A) and (R) are true and (R) is not correct explanation of (A).
  3. C (A) is true, but (R) is false.
  4. D (A) is false, but (R) is true.
Previously asked in CBSE board exam
2024 31/3/1 Q19
Generated by claude-sonnet-4-6 · 2026-06-15 06:54 · grounding rag
Model Answer

Option C — (A) is true, but (R) is false.

Assertion is correct, but the Reason is wrong: red light is least scattered (not most), so it travels farthest without losing intensity, making it visible from a large distance.

Explanation

The textbook explicitly states: "The red is least scattered by fog or smoke. Therefore, it can be seen in the same colour at a distance." Blue light (shorter wavelength) is scattered the most. Students often confuse "visible from far" with "scattered the most" — actually the opposite is true. Least scattering = least loss of intensity = visible over greater distances.

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Previous-year CBSE Grade 10 board exam questions, organised by subject and chapter, each with a model answer — free to read and print.