Advance sunrise and delayed sunset :The Sun is visible to us about 2 minutes before the actual sunrise, and about 2 minutes after the actual sunset because of atmospheric refraction. By actual sunrise, we mean the actual crossing of the horizon by the Sun. Fig. 11.10 shows the actual and apparent positions of the Sun with respect to the horizon. The time difference between actual sunset and the apparent sunset is about 2 minutes. The apparent flattening of the Sunâs disc at sunrise and sunset is also due to the same phenomenon.
Due to atmospheric refraction there is apparent rise in the position of the Sun as depicted in the fig below.