Atmospheric refraction and Scattering of light

Atmospheric refraction and scattering of light is a natural phenomenon that occurs in the environment. The refraction of light caused by the Earth’s atmosphere layer is called atmospheric refraction. As light passes from one medium to another, a part of the light is absorbed by particles of the medium, and this is called the scattering of light. Both the topics of Atmospheric refraction and scattering of light are interrelated to each other, and it helps in understanding light concepts that occur in the atmosphere. 

Atmospheric refraction and scattering of light

The sunrise and sunset, which paints the sky in shades of colours, is due to the scattering of light. Likewise, the twinkling of stars and the reason it appears higher is due to the Phenomenon of atmospheric refraction. The Earth’s atmosphere consists of layers of both hot and cold air. The hot layer of air acts as an optically rarer medium for light rays, whereas the cold layer acts as a denser medium. As the rays of light pass through the atmosphere with a varying layer of air, it is refracted by the atmosphere. 

Atmospheric refraction: Comprehensive explanation of the concept 

It is the refraction of light by the Earth’s atmosphere.

• Atmospheric refraction occurs when the refractive index of a medium changes over time
• The refractive index of the hotter air is slightly lower than the refractive index of the cooler air above it because the hotter air is lighter (less dense)
• Apparent random wavering or flickering of objects seen through a turbulent stream of hot air rising is an effect of atmospheric refraction

The Phenomenon associated with Atmospheric refraction:

• Twinkling stars: The light from the stars reaches the eyes after passing through Earth’s atmosphere crossing different layers of air with different optical densities. However, the change of temperature conditions leads to a change in optical densities of different layers of air. Hence, the rays of light from the star are refracted to different degrees, and hence the path of refracted rays keep changing. The change in refraction changes the light intensity of the star
• Advance sunrise and delayed sunset: The Sun is visible about 2 minutes before the actual sunrise and about 2 minutes after the actual sunset. The apparent flattening of the sun’s disc at sunrise and sunset is also due to atmospheric refraction
• Mirage – This is another example of atmospheric refraction, which creates an optical illusion known as Mirage in the deserts during summers. As layers of air near Earth’s surface become hot during summers, they act as an optically rarer medium. The layer of air above Earth’s surface acts as an optically cooler medium as it is cooler. This creates an optical illusion

Scattering of light: Comprehensive explanation of the concept

As light travels from one medium to another, a part of the light is absorbed by the particles of the medium, resulting in the Phenomenon of scattering of light. The reabsorption and re-emission of light energy occur without a change in the wavelength. The air molecules smaller than the wavelength of the incident light absorb the energy from the incident energy and reemit the light energy. Phenomena such as the blue colour of the sky, the colour of water in the deep sea, the reddening of the sun at sunrise and the sunset are some of the results of the scattering of light. 

Tyndall Effect: A Phenomenon associated with scattering of light

When a beam of light strikes fine particles like smoke, tiny water droplets, suspended particles of dust and molecules of air, the beam’s path becomes visible, and light, after being reflected in a dispersed manner by these particles, reaches us.

• Light of shorter wavelengths is scattered by minute particles, while bigger particles scatter the light of longer wavelengths. While light or sunlight falls in the atmosphere, rays of light with longer wavelengths are not scattered by air molecules. As blue light has the shortest wavelength, it is scattered by air molecules and leads to the appearance of the sky being blue
• The dispersed light may seem white if the scattering particles are large enough

Conclusion 

Many phenomena occur in nature due to the Atmospheric refraction and scattering of light. As the rays of light pass through the atmospheric layer with varied densities, it passes through different densities, leading to an atmosphere. As light travels from one medium to another, a part of the light is absorbed by particles, causing scattering of light. The comprehensive notes on Atmospheric refraction and scattering of light give insights and understanding about how the phenomenon occurs and its impact.