Answer:
x = 3.6 10⁷ m
Explanation:
The speed of an electromagnetic wave is constant, in a vacuum its value is c = 3 10⁸ m / s, this speed decreases when entering a material medium,
v = c / n
where n is the refractive index, but in this case the refractive index of air is n = 1.00002. The refractive index of a vacuum is n = 1, so we can assume that the change in velocity is negligible.
For the calculation we can use the relations of the uniform motion
v = x / t
x = v t
let's calculate
x = 3 10⁸ 0.12
x = 3.6 10⁷ m
