What is meant by advance sunrise and delayed sunset? Draw a labelled diagram to explain these phenomena.
Advance sunrise and delayed sunset is due to atmospheric refraction. When the sun is slightly below the horizon, the sunlight coming from the less dense (vacuum) to more dense (air) medium is refracted downwards. So the sun appears to be above the horizon. Similarly, even after actual sunset, the sun can be seen for a few minutes due to refraction of sunlight.
