Practice portal › Ray Optics and Optical Instruments › Refraction and Total Internal Reflection
Asked in GUJCET 2023 · Snell's law, slabs and apparent depth
Idea: the refractive index of a medium with respect to vacuum is n = c/v, the speed of light in vacuum divided by its speed in the medium.
Air is extremely thin, so light is slowed only very slightly and n sits just above 1.
The measured value at ordinary temperature and pressure is 1.00029.
That is why air is treated as 1 in school calculations, while the tiny excess is exactly what produces atmospheric refraction -- the sun seen a little before it has actually risen.
So the refractive index of air with respect to vacuum is 1.00029.
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