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Interactive Primary Newsletter 34 Nothin' but blue sky.... |
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Why is the sun red at sunset? At sunset, the sun appears red or orange rather than yellow (Fig. 5). Why is this the case? Again, the explanation comes down to the scattering of light by air particles.
Figure 5 - Sun appears orange/red in some sunsets In the summer at midday the sun’s rays only have to travel through about 100 km of atmosphere to reach the observer. However, when the sun is setting, the rays of light from it have to travel through about 1000 km of the earth’s atmosphere to reach the observer (Fig. 6). As the sunlight travels through this great thickness of atmosphere, blue light and to a lesser extent green and yellow light is scattered out of the rays by air particles. By the time the beam of light reaches the observer it is depleted in blue, green and yellow and the sun appears red/orange.
Figure 6 - When the sun is setting, the rays of light from it have to travel through about 1000 km |
