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.
\( \mu_{\mathrm{water}} \approx 1.33,\quad \mu_{\mathrm{glass}} \approx 1.5,\quad \mu_{\mathrm{diamond}} \approx 2.4 \)
\( v_{\mathrm{water}} \approx 2.25\times10^{8}\,\mathrm{m\,s^{-1}},\quad v_{\mathrm{glass}} \approx 2.0\times10^{8}\,\mathrm{m\,s^{-1}},\quad v_{\mathrm{diamond}} \approx 1.25\times10^{8}\,\mathrm{m\,s^{-1}} \)
So the speed decreases in the order water, glass, diamond.
Note: The same question was also asked in CUET (UG) 2023 on 13-06-2023 (Slot 1).