PART - 3 CH - 9 Light-Reflection and Eefraction — Science STD 10 — Question

The speed of light in vacuum is a fundamental constant of nature.
→ It is represented by c.
→For all ordinary purposes, the speed of light in vacuum is taken as c=3x10⁸ms^-1
In air, the speed of light is only marginally less, compared to that in vacuum.


→Therefore, speed of light in air is taken as 3 x 10⁸ ms^-1.
→The refractive index can be linked to an important physical quantity, the relative speed of propagation of light in different media
It turns out that light propagates with different speeds in different media.
→Consider a ray of light travelling from medium 1 into medium 2, as shown in figure 9.35.
→ Let v₁ be its speed in medium 1 and v₂ its speed in medium 2.
→The refractive index of medium 2 with respect to medium 1 is given by the ratio of the speed of light in medium 1 to the speed of light in medium 2.
→This is denoted by n_21.
...(9.12)
→By the same argument, the refractive index of medium 1 with respect to medium 2 is represented as n₁₂ It is given by
....(9.13)