Why is the sky blue?
The sky is blue because shorter-wavelngth blue radiation is scattered more by the air than other colors.
The sky is blue because light from the sun, which contains all colors, is scattered by the air. It turns out that blue light is scattered more than other colors. If there were no scattering, the sky would be black.
The molecules in the air scatter all colors of light, but tend to scatter shorter wavelengths more than longer wavelengths. Light is a wave, and the color of the light corresponds to different wavelengths. A rainbow separates light according to wavelength: red, orange, yellow, green, blue, violet. Air molecules are very small, so they scatter light this way, as do very small dust particles and water droplets. This is called Rayleigh scattering, named
after the physicist John Strutt (Lord Rayleigh) who first explained why the sky is blue.
Rayleigh scattering is the scattering of a wave from a particle whose diameter is much smaller than the wavelength of the wave. If the wave is a light wave, and the particle is a very small dust particle or water droplet, this condition is satisfied. (It is also satisfied by random density fluctuations in the air, so that the local air acts like the surrounding air with the extra air acting like a particle.)
You can imagine the electric field in the light wave causing charges in the particle to oscillate. Those oscillating charges radiate light at the same wavelength, but in all directions. This radiated light adds to the light originally passing through. Rayleigh showed that the net effect is the re-radiation of light at "sideways" angles.
Moreover, he showed that shorter wavelengths (shorter, but still large compared to the molecules) are scattered more strongly. The scattering strength is proportional 1/{fourth power of the wavelength}. This strong wavelength dependence arises from the nature of electric dipole radiation. The wavelength dependence means, for example, that blue light scatters about ten times as strongly as red light.
Large particles scatter all colors equally well; that is why clouds are white. They consist of large water drops or ice crystals. Likewise, when the sky is hazy, it is white because the particles in the air (aerosols, not molecules) are large and scatter light as clouds do.
This was originally written by a recent associate whose name I forget.
The sky appears blue due to a phenomenon known as Rayleigh scattering. Here's a step-by-step explanation:
1. Sunlight is composed of different colors of light, which vary in wavelengths. These colors include red, orange, yellow, green, blue, and violet.
2. The Earth's atmosphere contains tiny molecules, such as oxygen and nitrogen, as well as other particles like dust and water droplets.
3. When sunlight reaches the Earth's atmosphere, its shorter blue and violet wavelengths are scattered in all directions by the molecules and particles in the air. This scattering is more intense for shorter wavelengths due to a phenomenon called Rayleigh scattering.
4. The scattered blue light is then visible to our eyes when we look in all directions.
5. Additionally, our eyes are more sensitive to blue light compared to violet light, which contributes to the perception of the sky as blue.
It's important to note that this explanation simplifies the complex physics behind the sky's color, but it provides an overview of the major factors at play.
The sky appears blue due to a phenomenon called Rayleigh scattering. To understand why this happens, let me explain the process.
Sunlight is made up of different colors, which are wavelengths of light. When sunlight enters Earth's atmosphere, it interacts with the molecules in the air, such as nitrogen and oxygen. These molecules are much smaller than the wavelengths of light.
Now, the shorter wavelengths of light, like blue and violet, are scattered more than the longer wavelengths, like red and orange. This scattering is called Rayleigh scattering. The reason for this is that the blue and violet light waves are closer in size to the molecules in the air, so they interact more.
As a result, when sunlight reaches our eyes, the blue and violet light scatters in all directions and is more likely to reach our eyes from all parts of the sky. This gives the sky a blue color. On the other hand, the longer wavelengths, like red and orange, are scattered much less. Therefore, they continue on a more direct path, which is why the sun often appears yellow or red during sunrise or sunset when its light has to travel through a larger portion of Earth's atmosphere.
So, in simple terms, the sky is blue because the shorter blue and violet wavelengths of light are scattered in all directions by the molecules in the Earth's atmosphere.