\textbf{Case study (total internal reflection):} When a ray travels from a denser to a rarer medium and the angle of incidence exceeds the critical angle, it is totally internally reflected. — A ray of light travels from a medium into water at an angle of incidence of 18∘. The refractive index of the medium is more than that of water and the critical angle for the interface between the two media is 20∘. Which one of the following figures best represents the correct path of the ray of light?
(A)Figure A✓ Correct
(B)Figure B
(C)Figure C
(D)Figure D
Answer: (A)
Solution
Here the angle of incidence 18∘ is \emph{less} than the critical angle 20∘, so there is no total internal reflection: the ray is refracted (bending away from the normal into the rarer water), with a weak partial reflection. This corresponds to Figure A.
CBSE Class 12 Board · 2022 · Single correct option
