At sunrise and sunset, the sky will be partially colored red, blue sky, and polarized sky light (at least partially). This phenomenon can be explained on the basis of light scattering by atmospheric molecules. Scattering of light by the Earth's atmosphere depends on the wavelength. For particles much smaller than the wavelength of light (such as air molecules), particles are not a major obstacle to long wavelengths than for short. Scattering is reduced, red and orange light is scattered less than blue and purple, which is the cause of the blue sky. At sunset, on the other hand, solar light beam passes through the atmosphere maximum length. Lots of blue that has been issued by scattering. The light that reaches the earth's surface means less blue, which is the reason reddish sunset.
Only blue sky during the day. There are several reasons why the sky is blue then. Earth shrouded air layer called the atmosphere. Although not visible, the air is actually made up of tiny particles. Light from the sun is scattered by small particles in the atmosphere. But we know, the light of the sun is composed of a blend of all colors, from red, yellow, green, blue, to purple. The colors that have different frequencies. Red has a smaller frequency of yellow, yellow is smaller than the green, green is smaller than the blue, blue is smaller than purple. The greater the frequency of the light, the stronger the light that is scattered. The sky is partly dissipated sunlight. Because most widely dissipated is high frequency color (green, blue, and purple), the sky has a mix of colors, which when combined into a bright blue. Because many blue color dissipated, the white color of the sun is not perfect, as it should have happened if all the colors combined. The color of the sun becomes a little bit orange. In the afternoon, the sun often turns red. At that time, the sun already slanted travel longer distances to reach our eyes, so that more light is scattered. So that many left is a low-frequency light, which is red.
In the month and on the planet that does not have the atmosphere, sunlight is not scattered, so the sky is always black, even in daylight. Tyndall effect can also explain why the sky is blue during the day, whereas when the sun sets on the western horizon is orange or red. This is due to the scattering of sunlight by colloidal particles in space, and not all sunshine frequency dissipated with the same intensity. Therefore, the light intensity is directly proportional to frequency, then when the sun passed over us, the higher the frequency of the lot up to our eyes, so that we see the blue sky.
When the sun was about to set, the frequency of light scattering that low, that more up to us, so we watched the sky is orange or red. We recall strands visible light in the light spectrum, red-orange-yellow-green-blue-purple. From red to purple sequence, the higher the frequency. So the colors are approaching red light has a high frequency, and the colors are approaching violet light has a lower frequency.