The speed of light in vacuum is \( 3\times10^{8}\,\mathrm{m/s} \). The refractive index of material x is 1.8. The speed of light in material x would be
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 1.67\times10^{8}\,\mathrm{m/s} \)
The absolute refractive index of a medium is the ratio of the speed of light in vacuum to its speed in the medium.
\( \displaystyle n = \frac{c}{v} \;\Rightarrow\; v = \frac{c}{n} \)
\( \displaystyle v = \frac{3\times10^{8}\,\mathrm{m/s}}{1.8} = 1.67\times10^{8}\,\mathrm{m/s} \)