Question

What is meant by scattering of light? Use this phenomenon to explain why the clear sky appears blue or sun appears reddish at sunrise.

Answer 1

Step 1: Definition of scattering of light

Scattering of light is the phenomenon of change in the direction of light on striking particles like water droplets, dust particles, smoke, etc.

Step 2: Explanation

The blue color of the sky

1. The color of the sky looks blue due to the scattering of light in the Earth's atmosphere. The atmosphere consists of particles of smoke, water droplets, and suspended dust particles.
2. These particles have sizes smaller than the wavelength of visible light. They are more effective in scattering light of a shorter wavelength than the light of a longer wavelength.
3. So, the finer particles present in the air scatter the blue light (shorter wavelength) more strongly and effectively than the red light. The scattered blue light enters our eyes. Hence, the sky appears blue.

Reddening of the sun at sunrise

1. At the time of sunrise or sunset, the sun is near the horizon. Light rays from the sun which are near the horizon have to pass through a larger distance through Earth's atmosphere before reaching our eyes.
2. The sunlight has to travel a large distance through Earth's atmosphere, it passes through a large number of particles suspended in the air. Near the horizon, most of the blue light and other lights of shorter wavelengths are scattered by these particles.
3. The red light which has the largest wavelength is scattered the least. Among the colors of sunlight, red color is scattered the least and enters our eyes. This gives rise to a reddish appearance of the sun.