Tag: physics

We see red colour of the sun at sunrise or sunset as the sun at horizon and light rays need to travel a greater distance. In the process of scattering, violet, blue and green rays in the original sunlight are removed and the transmitted beam has yellow and red dominant.

Red light is used as danger signal because it is having high wavelength, less scattering ,hence can travel larger distances.

Blue light is scattered the most. Hence, as sunlight travels the earth, most of the blue colour is scattered and hence spread. This causes the sky to appear blue in the day.

Raman effect is an example of incoherent scattering of light, as it is specific to the molecule which cause it.

The Tyndall effect occurs when light is scattered by particles in a colloid or fine suspension. This phenomenon is most pronounced when the size of the particles is comparable to the wavelength of the incident light.

In a vacuum or empty space, all electromagnetic waves, including all colors of visible light, travel at the same constant speed (the speed of light, c).

Answer is D.

The rainbow is caused by light from the sun (or moon) interacting with raindrops falling from the air. These raindrops are mostly round. A ray of light entering such a droplet is bent (refracted) and decomposed into all possible colors (wavelengths) which the white light consists of. The ray then reflects internally in the droplet, and emerges roughly into the direction it came from when it entered the drop. Since the rays of the different colors all exit at slightly different directions, we see a color band in the sky.
The colors are produced by a phenomenon called dispersion. Dispersion causes white light, which consists of all possible colors to break up into all components, when the light travels from one medium (e.g. air) to another (e.g. water). The different colors of light have all slightly different directions, so if we look in a certain direction in the sky we can see the spectrum.

C. The blue colour of sky is due to scattering of light   = correct statement

The blue colour of sky is due to the scattering of light by small particles of the atmosphere (air molecules) when the light is incident on particles whose size is smaller than the wavelength of light, it is scattered.

According to Rayleigh law, the intensity of scattered light is inversely proportional to the fourth power of wavelength.

Option C is correct answer.

During sunset and sunrise, the rays have to travel a larger part of the atmosphere because they are very close to the horizon. Therefore, light other than red is mostly scattered away. Most of the red light, which is the least scattered, enters our eyes. Hence, the sun appear red..