When the sun is either rising or setting and appears to be just in the horizon, it is in fact below the horizon. The explanation for this seeming paradox is that light from the sun bends slightly when entering the earth's atmosphere as shown in figure. Assume that the atmosphere has uniform density and hence uniform index of refraction n and extends to a height h above the earth's surface, at which point is abruptly stop. The angle `delta` above the Sun's true position is given by

We can see the Sun even when it is little below the horizon because of

When the sun appears to be just on horizon, it is in fact below the horizon. This is because the light from the sun bends when it enters the earth’s atmosphere. Let us assume that atmosphere is uniform and has index of refraction equal to mu . It extends upto a height h (lt lt R = radius of earth) above the earth’s surface. In absence of atmosphere how late would we see the sunrise compared to what we see now? Take time period of rotation of earth to be T. Calculate this time for following data R = 6400km, mu = 1.0003, h = 20 km, T = 24hr .

Deoes the atmospheric pressure vary with the height above the earth's surface?

The height from the surface of earth and electron density of D layer of earth's atmosphere are

We can see the sun even when it is little below the horizon because of ....

Assuming earth to be a sphere of a uniform density, what is the value of gravitational acceleration in mine 100km below the earth's surface (Given R=6400km)