05-01-2018, 04:33 PM
*The red colour in rainbow is seen at an angle of 42.8° and that of violet is at 40.8°.
*Colour at the centre of rainbow - Green
*When we look from the outer space rainbow is seen as a circle. But when we look from the earth, rainbow is seen as semicircle.
Interference
* The distribution of light energy when two or more lightwaves superimpose to each other is called interference.
*The different colours in soap bubbles is due to Interference of light.
*Colours that appear on the upper layer of oil spread on road is due to
Ans : Interference.
* Holography is a technique of recording and reproducing three dimensional images based on the principle, interference of light. The 3D images thus produced are called holograms.
* Interference pattern using light waves was first observed by a British Physicist, Thomas Young.
Diffraction
*When light passes through a very small object (ie, sharp edge, slit, wire etc), it spreads out into the geometrical shadow of the obstacle. This process is known as diffraction of light.
*The projector in a film theatre works on the principle
Ans : Diffraction.
* Rings around the sun is due to
Ans : Diffraction
*The optical phenomenon which causes fringe pattern of CD is
Ans : diffraction
Scattering of light
*The blue colour of the sky is due to -Scattering
*Reddening of sun at sunrise and sunset occurs due to the scattering of light.
*Light of shorter wavelength is scattered more than the light of longer wavelength.
*The colour which scatters most
Ans : Violet
*The colour which scatters least
Ans : Red
*More reflection and less scattering of light occurs from most objects, leads to brighter appearance of coloured bodies.
*The colour used in fog lamp of vehicles
Ans : yellow light
*In winter or rainy season light rays are scattered most. So we use yellow coloured fog lamp as the yellow colour scatters least.
*For an astronaut on moon sky appears in black colour due to the absence of scattering of light as there is no atmosphere in moon.
*Blue colour of the sky and yellow tone of the sun are due to
Ans : Rayleigh Scattering
Polarisation
*The phenomenon of confining the vibrations of a transverse wave to a particular direction is called
Ans : Polarisation.
*A natural polarising material is Tourmaline
*Nicol prism is a polaroid.
*Polaroids are used in windows of aeroplanes and cars, sun glasses, three dimensional motion pictures, oil paintings to improve the colour contrast.
