Question

Why is the sun visible to us 2 minutes before the actual sunrise , and also about 2 minutes after actual sunset ?

Explain in detail !

CLASS 10

Answer 1

    The Sun is visible to people on Earth about 2 minutes before the Sun rises above the horizon. Also we are able to see the Sun for about 2 minutes after the Sun goes below the horizon.  This is due to the Refraction of light rays from Sun.

   The layers of air in the atmosphere have different densities. The difference is due to composition, pressure, and temperature. At Sunrise and Sunset the main effect is due to temperature. Hot air is less dense and has a smaller refractive index.

   Due to difference in the refractive indices between the layers, the light rays bend towards the people on the surface of Earth. So we are able to see Sun even though in reality Sun is below the actual line of sight (horizontal line or the horizon).  

   The light rays bend upwards (away from normal) when the density of upper layer is more than that of the lower layer.  The light rays bend downwards (towards the normal) when the density of upper layer is less than the lower layer. 

Answer 2

☣️REFRACTION☣️

☣️☣️Due to the phenomenon of atmospheric Refraction , The sun is visible before actual sunrise abd after actual sunset. The density of atmospheric layer and Hence, the refractive index of atmospheric layer also decreases....

⚛️⚛️The light ray travel through rarer to denser layer starting from the sun, they bent more and more towards the Normal...

☣️☣️Thus, the sun appears to rise about 2 minutes earlier and for the same reason it appears to set by 2 minutes...