scattering of light Flashcards
what is a colloidal solution
Colloidal solutions, or colloidal suspensions, are nothing but a mixture in which the substances are regularly suspended in a fluid.
what is scattering of light
the phenomenon of absorption of light and reradiating it in a different direction is called as scattering of lgiht.
Scattering of light is a phenomenon of change in the direction of light on striking particles like an atom, molecule, dust and water droplet etc
what are the conditions necessary for scattering of light
-when the size of the particle matches the wavelength of light, the particle absorbs the light and then scatters it.
-the atom or particle scattering the light is called the SCATTERER. If the size of the scatterer is very small,then violet/indigo/blue light is scattered the most.
- the size of the particle is large, then red colour is scattered
- if the size of the particle is relatively large, then white colour light is seen.
why do colloidal solutions scatter light but not true solutions
a beam of light passing through the true solution is not seen because the size of the particles are very minute. The beam of light passing through the colloidal solution is seen because the size of the particles is relatively larger.
describe the earth’s atmosphere wrt a colloidal soln
the earth’s atmosphere is a heterogenous mixture of minute particles. these minute particles include smoke, tiny water droplets, suspended particles of dust and molecules of air.
explain tyndall effect
When a beam of light strikes colloidal particles they scatter light falling on them in all directions making the particles illuminated. This phenomena is called as Tyndall effect.
what does colour of scattered light depend upon
The colour of the scattered light depends on the size of the
scattering particles. Very fine particles scatter mainly blue light while
particles of larger size scatter light of longer wavelengths. If the size
of the scattering particles is large enough, then, the scattered light may
even appear white.
why is the colour of the sky blue
the molecules of air and other fine particles present in the earth’s atmosphere have size smaller than the wavelength of visible light. These are more effective in scattering the light near the blue end which have shorter wavelength than those near the red end which have longer wavelength. The wavelength of red light is 1.8 times greater than that of blue light. So these particles scatter the blue light (shorter wavelength) more strongly than the red light( longer wavelength). This scattered blue light reaches our eyes and the sky appears blue.
what would happen if the earth had no atmosphere
if the earth had no atmosphere, theere would be no gas present in the atmosphere. There will be scatterers of light the cause the scattering of light. So due to the absence of scattering of light, the sky will appear dark.
why is the sky appear darker to the passengers flying at higher altitudes
As we move up to very high altitudes the atmosphere becomes thinner. The particles present here are very less. So, scattering of light is prominent at such heights. Thus the sky appears dark to passengers flying at very high altitudes.
why cant the astronaut see the atmosphere
When Astronauts fly at higher altitudes, the sky appears dark because, at very high altitudes, there is no atmosphere. So, there would not have been any scattering of light.
clouds are white in colour
clouds are made up of water droplets of different sized. these water droplets of different sizes scatter light of different colour ie the smaller droplets scatter blue and the larger droplets scatter green/red. Since all the colours are scattered by the droplets, the resultant colour is white.
why is the sun red at sunrise and sunet
during sunrise and sunet, the sun appears red because the sunlight is near the horizon and the sunlight needs to travel a longer distance. During this long travel, the shorter wavelength component of light gets scattered away, and the red light, with a longer wavelength can travel for longer distances without getting scattered, reaches our eyes.
why does the sun looks white at noon
during noon, the sun overhead and the sunlight has to travel a relatively shorter distance. So during this travel only a little of the blue and violet components are scattered away. So the sun loks white.
why do we add sodium thiosulphate and conc. h2so4 to the
the chemical reaction between sodium thiosulphate and concentrated sulphuric acid gives colloidal sulphur
