### Theory:

In the previous section, we have discussed atmospheric refraction. In this section, we will see the advanced sunrise and delayed sunset.

Advanced sunrise and delayed sunset are events caused due to atmospheric refraction.

Because of atmospheric refraction, the Sun is visible to all of us about $$2\ minutes$$ before and after the actual sunrise and the actual sunset, respectively.

By actual sunrise, we mean the actual crossing of the horizon by the Sun. The below figure displays the actual and apparent positions of the Sun with respect to the horizon. The time difference between the actual 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.

Atmospheric refraction effects at sunrise and sunset