⚛️ Physics · Ray Optics and Optical Instruments · NEET & JEE

Critical angle in a medium is 45 degrees. Refractive index is:

Answer: sqrt(2).

A 1
B sqrt(2)
C 2
D 1/sqrt(2)

Correct answer: B. sqrt(2)

Explanation: sin(C) = 1/n. sin(45) = 1/sqrt(2) = 1/n. n = sqrt(2) = 1.414.

Concave mirror ray diagram with an object drawn as a candle on the principal axis, the focal point F marked, and the parallel ray and focal ray reflecting to form an inverted real image

Concave mirror ray construction: a ray parallel to the axis reflects through F, and a ray through F reflects parallel, locating the inverted real image. Image: Maxmath12, CC0, via Wikimedia Commons.

Concept context

Reflection, refraction, lenses, mirrors, total internal reflection.

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Critical angle in a medium is 45 degrees. Refractive index is:

Concept context

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