The Brewster's angle for air to glass interface when an unpolarised light is incident on a glass (\( n = 1.5 \)), such that reflected and refracted rays are perpendicular to each other, is nearly:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( i_B = 57^\circ \)
When the reflected and refracted rays are perpendicular, the angle of incidence is the Brewster's angle, and the reflected light is completely polarised. Brewster's law gives
\( \displaystyle \tan i_B = n \)
\( \displaystyle i_B = \tan^{-1}(1.5) \approx 56.3^\circ \approx 57^\circ \)
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Polarisation by Reflection – …
