Question

Why is the refrative index of atmosphere different at different altitudes.​

Answer 1

Assuming that you meant refractive index the answer is

refractive index of a medium is the ratio of velocity of light in vacuum to velocity of light in that medium .

as you know, atmosphere is the mixture of many medium because many gases contain in atmosphere which densities are different and velocity of light in that gases are different .

so, when light passes through atmosphere velocity is different at different layers ( altitudes).

hence, refractive index of atmosphere is different at different altitudes.

Hope this helps (:

Answer 2

$\huge\tt{ANSWER:}$

As we move above the Earth’s surface, the density of air goes on decreasing. There is a gradual increase in the refractive index from the atmosphere to the Earth’s surface. Thus, the refractive index of the atmosphere is different at different altitudes.