The velocity of light in diamond, glass and water decreases in the following order:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Water > glass > diamond
The speed of light in a medium of refractive index \( \mu \) is \( v = c/\mu \), so the larger the refractive index, the smaller the speed.
\( \mu_{\mathrm{water}} \approx 1.33,\quad \mu_{\mathrm{glass}} \approx 1.5,\quad \mu_{\mathrm{diamond}} \approx 2.4 \)
Since \( \mu_{\mathrm{water}} \lt \mu_{\mathrm{glass}} \lt \mu_{\mathrm{diamond}} \), the speeds are in the order \( v_{\mathrm{water}} \gt v_{\mathrm{glass}} \gt v_{\mathrm{diamond}} \). A decreasing order of speed starts with water.
Note: The same question was also asked in CUET (UG) 2023 on 12-06-2023 (Slot 3).
NCERT (2026-27):
Total Internal Reflection – …
