Scattering of light | Tyndall Effect | Blue colour of Sky | The red colour of the sun at sunrise and sunset
What is Scattering of light?
Scattering of light is the phenomenon in which light rays deviate from their straight path due to the presence of particles or irregularities in the medium they pass through.
The amount of scattering depends on the wavelength of the light and the size of the particles. Shorter wavelengths and higher frequencies scatter more than longer wavelengths and lower frequencies. For example, blue light has a shorter wavelength than red light, so it scatters more in the atmosphere.
What is Tyndall effect?
The Tyndall effect is the phenomenon in which light is scattered by particles in a colloid or in a very fine suspension. A colloid is a mixture in which one substance is dispersed as very small particles in another substance, such as milk, fog, or smoke. A fine suspension is a mixture in which solid particles are suspended in a liquid or a gas, such as dust or pollen in the air.
The Tyndall effect occurs when a beam of light passes through a medium containing such particles and collides with them, causing the light to deviate from its original path and become visible.
The amount of scattering depends on the wavelength of the light and the size of the particles. Shorter wavelengths, such as blue and violet, are scattered more than longer wavelengths, such as red and orange. This is because shorter wavelengths have more chances of interacting with the particles than longer wavelengths.
Some examples of the Tyndall effect are:
Why is blue colour of the sky.
The blue colour of the sky is due to Rayleigh scattering of sunlight by the molecules of air in the atmosphere. Rayleigh scattering is the scattering of light by particles that are much smaller than the wavelength of light.
The amount of scattering is inversely proportional to the fourth power of the wavelength, which means that shorter wavelengths are scattered more than longer wavelengths. Since blue light has a shorter wavelength than red light, it is scattered more by the air molecules and reaches our eyes from all directions, making the sky appear blue.
Reason behind The red colour of the sun at sunrise and sunset
The red colour of the sun at sunrise and sunset is due to a phenomenon called Rayleigh scattering. This means that when sunlight passes through the Earth's atmosphere, the blue and violet light is scattered more than the red and orange light, leaving more of the latter to reach our eyes.
When the sun is low in the sky, like at sunrise and sunset, the sunlight has to travel through more atmosphere than when it is high in the sky, like at noon. This means that more blue and violet light is scattered away, making the sun appear red or orange.
The sun does not appear red at noon because the sunlight has to travel a shorter distance through the atmosphere, and most of the yellow, orange and red light passes through while a small amount of blue and purple light is scattered and removed from the mix.