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

For a medium of refractive index 1.5, the critical angle for total internal reflection is about:

Answer: 41.8°.

A 30°
B 41.8°
C 48.6°
D 60°

Correct answer: B. 41.8°

Explanation: sinθ_c = 1/n = 1/1.5 = 0.667, so θ_c ≈ 41.8°.

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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For a medium of refractive index 1.5, the critical angle for total internal reflection is about:

Concept context

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