When the sun goes down, why is there red light on the horizon?

Sunlight refracts through the prism, and white light becomes red, orange, yellow, green, blue, blue and purple; The density of the atmosphere is different at different heights, and it gradually decreases from the ground to the sky, which can be regarded as a prism; When the sun goes down, among the seven colors refracted into the air, red light has the largest wavelength and the strongest penetrating power, and the most red light is emitted into the air through clouds, so red light appears in the sky.

Before and after sunrise and sunset, there are often colorful atmospheric images in the sky, which is summer. According to the time of appearance, it is also called sunrise or sunset. The direction and color of sunset glow are influenced by the position of the sun, the distribution of water vapor and aerosol in the air, the amount and shape of clouds.

Light has both wave-particle duality and energy. If it is a wave, it is a capacitive wave, not a mechanical wave. We all know that sunlight is a combination of seven basic lights, of which red light has the longest wavelength. According to the nature of the wave, the longer the wavelength, the stronger the diffraction ability and the larger the object that can climb. Therefore, we can see more red light when the sun is occupied by the earth.

Extended information Most of the light sources we come into contact with in our life are not point light sources, that is to say, the direction of emission is not single, such as the sun, light bulbs, cell phone flashlights. Their irradiation direction is a range, and they cannot form a straight light path. But common sense tells us that people will form shadows when standing in the sun, and they will not see the main body of the sun when there is an eclipse. This seems to indicate that light cannot bypass the object in front and travel along a curve, but only along a straight line, so the propagation path of light is often abstracted into a straight line with arrows. In other words, "walking straight" is a summary of people's experience in life practice.

If there is no obstacle ahead, light does travel in a straight line, but what happens if it touches an object? We also observe from life that light will reflect when it meets an object, just like a basketball will rebound when it hits the ground. When the incident direction is fixed, the rebound direction of basketball is the same every time it hits the flat ground, and the exit direction is symmetrical with the incident direction, but we don't know which direction the basketball will rebound when it hits the uneven ground. We call the former "specular reflection" and the latter "diffuse reflection".

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