Rayleigh: Scattering of Light

Rayleigh scattering is a physical phenomenon that describes the scattering of electromagnetic radiation by particles much smaller than the wavelength of the radiation. This scattering is responsible for the blue color of the sky, the reddening of the sun at sunset, and other atmospheric phenomena. This phenomenon occurs when light interacts with particles smaller than its wavelength, causing the light to scatter in all directions. The amount of scattering depends on the size of the particle, the wavelength of the light, and the refractive index of the particle. In the case of Rayleigh scattering, the scattered intensity is inversely proportional to the fourth power of the wavelength, which means that shorter wavelengths (blue light) are scattered more strongly than longer wavelengths (red light). This explains why the sky appears blue during the day, as the blue light from the sun is scattered more efficiently by the air molecules. As the sun sets, the light has to travel through more atmosphere to reach our eyes. This means that more of the blue light is scattered away, leaving behind the longer wavelengths of red and orange, which is why the sky often appears red at sunset.
Rayleigh scattering is a fundamental phenomenon in physics, with important applications in various fields, including atmospheric science, optics, and telecommunications. The scattering of light by air molecules is crucial for understanding the Earth's atmosphere and its effects on climate. It also plays a role in optical communications, where it can cause signal loss and degradation. The study of Rayleigh scattering has led to the development of various optical techniques for measuring atmospheric properties, such as the concentration of air molecules and the size distribution of aerosols. This understanding has improved our ability to predict weather patterns and monitor air quality.