About scattering in raindrops
- Regular scattering of light in raindrops results from both refraction and chromatic dispersion.
- Regular scattering occurs when light is scattered by particles that are much smaller than the wavelength of the radiation.
- Refraction occurs when light changes speed and direction as it passes from one transparent medium to another.
- Chromatic dispersion is the phenomenon where light separates into its various colours and becomes visible to a human observer.
- Scattering in raindrops obeys the laws of both reflection and refraction, commonly referred to as Snell’s law.
Here are three related descriptions of what causes scattering when visible light strikes a raindrop:
- When light of a specific wavelength strikes the surface and enters a raindrop its subsequent path depends upon the point of impact, and the refractive indices of water and air.
- When rays of light of a single wavelength strike a raindrop at different points, scattering is primarily determined by the angles at which they enter the droplet.
- The interaction between refraction and chromatic dispersion gives rise to the appearance of rainbow colours when parallel white light rays strike various points on the surface of a raindrop.
About random scattering
- Random scattering refers to the scattering of light rays in various directions when they encounter irregularities or imperfections on a surface.
- Random scattering takes place when a material reflects or transmits light rays in multiple directions.
- Random scattering can produce reflections that appear soft, lack distinct detail, or even result in no reflection at all.
- When light passes through sheets of glass with irregular yet smooth surfaces, it distorts the view of the world beyond. Random scattering is responsible wherever the image appears blurry and confused.
- A reflection that is free of the effects of random scattering is called a specular reflection. Mirrors generally produce specular reflections.
- Diffuse light involves the random scattering of light in all directions when it encounters a rough or uneven surface.
- Diffuse light is produced when it bounces off rough or uneven surfaces, scattering light in every direction.
- Diffuse light can be the result of the overall structure and composition of the medium, such as when light is transmitted through the interior of a medium that:
- Contains foreign material
- Contains suspended particles of different sizes
- Has an irregular interior structure
- Has variations in density
- Absorbs light and then re-emits it
- Translucent materials containing dissolved substances such as dyes don’t cause random scattering.
- On a microscopic scale, all objects adhere to the law of reflection; however, when surface irregularities are larger than the wavelength of light, the light undergoes scattering leading to diffusion.