A white light falls on a prism. Among given choices which light bends the least
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Red
The refractive index of glass is different for different colours, and it is smallest for red (the longest wavelength) and largest for violet. For a thin prism the angle of deviation is \( \delta = (\mu - 1)A \), so the colour with the smallest \( \mu \) is bent the least.
The colours in the options, in order of increasing wavelength, are blue, green, yellow, red. The refractive index decreases along this order, so red bends the least and blue the most.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), but it is still in the CUET 2026 syllabus, so do not skip it.
NCERT (Pre-rationalised edition, 2022-23):
Dispersion by a Prism – “… The red light bends the least, while the violet light bends the most (Fig. 9.25). The phenomenon of splitting of light into its component colours is known as dispersion.”