Rayleigh scattering is a physical phenomenon in which light (or other electromagnetic radiation) is scattered by particles much smaller than the wavelength of the light itself. This effect was first described in detail by the English scientist Lord Rayleigh in 1871.
In this process, light waves are scattered by molecules in the atmosphere or by other very small particles, without any change in energy. This results in a change in the direction of the light rays.
1. Causes of Rayleigh scattering
Scattering is caused by particles in the air or other medium being much smaller than the wavelength of light. It occurs primarily when light interacts with molecules in the air (such as oxygen or nitrogen molecules ) or with other small particles .
π Particles smaller than 1/10 the wavelength of light cause Rayleigh scattering, while larger particles, such as dust or soot, result in a different type of scattering (such as Mie scattering ).
2. How does Rayleigh scattering work?
Rayleigh scattering occurs when light waves encounter small particles, which scatter the waves in different directions. This results in a change in the light's direction , but without changing its energy .
π Important property : The amount of scattering is inversely proportional to the fourth power of the light's wavelength . This means that shorter wavelengths (such as blue light) are scattered much more strongly than longer wavelengths (such as red light) .
3. Example of Rayleigh scattering
One of the most striking examples of Rayleigh scattering is the blue color of the sky . Blue light has a shorter wavelength and is therefore scattered much more strongly by the molecules in the atmosphere than red or yellow light , resulting in the blue sky we see.
| Color light | Wavelength | Degree of scattering |
|---|---|---|
| Blue | 450-495 nm | Strong (high scattering) |
| Green | 495-570 nm | Average |
| Red | 620-750 nm | Weak (low scattering) |
π The sky appears blue because the blue wavelengths are scattered more strongly by the atmosphere.
4. Applications of Rayleigh Scattering
Rayleigh scattering affects many natural and engineering phenomena:
| Application | Description |
|---|---|
| π Blue sky | Blue light is scattered more strongly , which gives the sky its blue color. |
| π Sunrise and sunset | Longer light (red/orange) is less scattered, causing the sky to appear red/orange at sunrise and sunset. |
| π Lighting and atmospheres | Rayleigh scattering affects how light propagates through the atmosphere, which is important for lighting and perception of colors in the sky. |
| π¬ Scientific applications | Rayleigh scattering is used to measure particle size in the atmosphere or liquids. |
π Rayleigh scattering is crucial for understanding the color of the sky and the distribution of light in the atmosphere.
5. Formula for Rayleigh scattering
The intensity of the scattering can be calculated using the formula:
whereby:
- = Intensity of the scattering.
- = Wavelength of light.
π The shorter the wavelength (blue light), the stronger the scattering.
π‘ In short :
Rayleigh scattering is the phenomenon whereby light is scattered by particles much smaller than the wavelength of the light itself , resulting in the sky appearing blue and the stronger scattering of shorter light, such as blue, compared to longer light, such as red. It is used in atmospheric science , lighting , and optics .