Question

Assertion: Diamond are known for their spectacular brilliance, but diamonds found in nature rarely exhibit the brilliance.

Reason: By cutting the diamond suitably, multiple total internal reflections can be made to occur.

• A. If both assertion and reason are true and reason in the correct explanation of assertion.
• B. If both assertion and reason are true and reason is not the correct explanation of assertion.
• C. If assertion is true but reason is false.
• D. If both assertion and reason are false.

Answer 1

Answer: (A)

If both assertion and reason are true and reason in the correct explanation of assertion.

Answer 2

• Assertion Analysis: Diamonds are renowned for their spectacular brilliance. However, diamonds found in nature (uncut, rough diamonds) typically appear dull and lack this brilliance. The brilliance is achieved after careful cutting and polishing. Thus, the assertion is true.

• Reason Analysis: The brilliance of a diamond is a result of its high refractive index (approximately 2.42) and the specific way it is cut. Due to the high refractive index, the critical angle for total internal reflection at the diamond-air interface is very small (around 24.4°). When a diamond is cut with precise facets, light entering the diamond can undergo multiple total internal reflections within its structure before exiting. This internal reflection and dispersion of light give the diamond its characteristic sparkle and brilliance. Thus, the reason is true.

• Relationship between Assertion and Reason: The reason directly explains why cut diamonds exhibit brilliance while natural ones do not. The act of "cutting the diamond suitably" (as stated in the reason) is precisely what allows "multiple total internal reflections to occur," which in turn creates the "spectacular brilliance" mentioned in the assertion. Therefore, the reason is the correct explanation for the assertion.