In the total internal reflection, light ray traveling through an optically denser medium to a rarer medium at the interface,
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → is completely reflected back to optically denser medium.
Total internal reflection occurs when light travelling in the denser medium meets the boundary with a rarer medium at an angle of incidence greater than the critical angle. There is then no refracted ray: all the light is reflected back into the denser medium.
\( \displaystyle \sin i_{c} = \frac{n_{\mathrm{rarer}}}{n_{\mathrm{denser}}} \)
Why the other options are incorrect
Option (2) is completely refracted to the rarer medium — Incorrect. Beyond the critical angle no light is refracted.
Option (3) is partially reflected and partially refracted. — Incorrect. Partial reflection with partial refraction happens below the critical angle, not in total internal reflection.
Option (4) is absorbed completely by the optically denser medium. — Incorrect. Nothing is absorbed at the boundary; the whole ray is reflected (which is why optical fibres carry light with little loss).
NCERT (2026-27):
Total Internal Reflection – “… If the angle of incidence is increased still further (e.g., the ray AO4), refraction is not possible, and the incident ray is totally reflected. This is called total internal reflection. When light gets reflected by a surface, normally some fraction of it gets transmitted. The reflected ray, therefore, is always less intense than the incident ray, howsoever smooth the reflecting surface may be. In total internal reflection, on the other hand, no transmission of light takes place.”