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

Critical angle for medium A (n=1.5) to medium B (n=1.2):

Answer: 53.1 degrees.

A 53.1 degrees
B 41.8 degrees
C 30 degrees
D No TIR since going to less dense

Correct answer: A. 53.1 degrees

Explanation: n_A > n_B so TIR is possible. sin(C) = n_B/n_A = 1.2/1.5 = 0.8. C = sin^-1(0.8) = 53.1 degrees.

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.

Read the full Ray Optics and Optical Instruments notes →

Critical angle for medium A (n=1.5) to medium B (n=1.2):

Concept context

More Ray Optics and Optical Instruments questions