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Ray Optics and Optical Instruments — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsRay Optics and Optical Instruments1 Mark
Question
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion: The diamond shines due to multiple total intemal reflections.
Reason: The critical angle for diamond is 24.4°.
✓

Answer

  1. Both A and R are true but R is not the correct explanation of A.

Explanation:

The brilliance of diamond is due to total internal reflection of tight. $\mu$ t for diamond is 2.42, so that critical angle for diamond air interface is C = 24.4° $\big($from sin $\text{C}=\frac{1}{\mu}\big).$ The diamond is cut suitable so that light entering the diamond from any face suffers multiple total internal reflections at the various faces and remains within the diamond Hence the diamond sparkles.

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