Reflection of light
Polarization of light
Refraction of light
Interference of light
The twinkling of stars is due to the passing of light from the stars to our eyes through the different layers of our atmosphere. Usually related to temperature gradient there is the change in density of air and due to this change in density when the light rays travel through layers having different densities only then the twinkling of stars is caused in most cases.
- Basically, the twinkling of stars is caused when light rays travel through different layers of the atmosphere and then finally reach the Earth’s surface. This twinkling is due to the refraction of light rays. It is generally related to the temperature gradients. As light rays from any star race through the atmosphere, it deviates and deflects through different layers, causing it to bend before you see it. In the atmosphere, there is a regular change in the density of air that increases as we travel towards the surface. Once the light from a star enters the Earth’s atmosphere, each of its rays get refracted, causing a slight change in the direction due to various temperature and density layers of the atmosphere. You can visualize that light moves in a zig- zag path instead of a straight path to your eyes in case the Earth didn’t have an atmosphere.
- Why do stars twinkle and planets do not? When the light from the stars enters the atmosphere, it collides with gas molecules and scatters (reflection and interference). Planets are a collection of a large number of point sources of light, whereas stars are considered to have a point source. We are able to see a tiny beam of light from it as the star is so far away from it. This light will get scattered from our eyes and then back into them, almost like it is blinking on and off. The process is so fast it appears like twinkling. As compared to stars, planets are closer to us and send more light; even if some light beams get scattered away, others get to us. So, planets do not usually twinkle.
Atmospheric refraction is the phenomenon where the light rays or other electromagnetic waves that pass through the atmosphere if the Earth deviates due to the variation in the density of air and function of height. Atmospheric refraction not only deviates the visible light rays that come from the stars but also deviates the electromagnetic waves in different directions. Not only the light, but the sound waves also get refracted when they pass through the different atmospheric layers. Atmospheric refraction can help you to locate the celestial bodies and the distant objects in the universe. This is due to this phenomenon only that the celestial bodies or other distant objects in the sky appear to be at a much higher position than they actually are.
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