Twinkling of stars
Light coming from the stars undergoes refraction on entering the Earth’s atmosphere. This refraction continues until it reaches the Earth’s surface. This happens because of uneven heating of atmospheric air. Hence, the atmospheric air has changing refractive index at various altitudes. In this case, starlight continuously travels from a rarer medium to a denser medium. Hence, it continuously bends towards the normal.
The refractive index of air medium gradually increases with a decrease in altitude. The continuous bending of starlight towards the normal results in a slight rise of the apparent position of the star.
Since the physical conditions of the Earth’s atmosphere keeps changing, the apparent position of the star is not stationary. The star changes its position continuously, which makes it twinkle. This happens because starlight travels a very large distance before reaching the observer. However, the path varies continuously because of uneven atmospheric conditions. Hence, the stars seem to be fluctuating, sometimes appearing brighter and sometimes fainter. All this together, gives rise to the twinkling effect of stars.
because the planets are near to us than the stars and while the light is getting reflected the area of planet is more so the reflection is cross ccut by each other and in case o fstars they are point szed and reflection is maximum. the color of sun in sunrise is red. this is because during sunrise the sun is near horizon and hence light has to cover maximum distance to reach our eyes due to which all the other colors except red light gets scattered in atmosphere and hence only red light reaches our eyes and gives us the sensation that sun is red
During the sunrise also in the sunset, the sun rays has to travel a greater distance through the atmosphere because of being slanted. In the solar spectrum the colors having higher wavelengths like red do not scatter much but the shorter wavelength like violet, blue etc, get scattered easily. So in case of sunrise, when the rays that has to travel a longer distance, the smaller wavelengths like blue, violet, green etc are scattered off in the upper atmosphere and the ray reach earth consists of longer wavelengths of orange and red. Thus, sky appears reddish.