Question

Name the atmospheric phenomenon due to which the sun can be seen above the horizon about two minutes before actual sunrise.

Answer 1

The phenomena is called refraction of light. Due to change in refractive index (property of the medium) of the atmosphere of earth the light bends when it goes from one medium to another medium because the change in speed of light in different mediums and due to this it bends and we see the sun before and after actual sunrise and sunset.

Comments

Atmospheric refraction
By actual sunrise, we mean the actual crossing of the horizon by the Sun. The time difference between actual sunset and the apparent sunset is about 2 minutes. The apparent flattening of the Sun’s disc at sunrise and sunset is also due to the same phenomenon. Hence, the length of day increases by 4 minutes.