Refraction
Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one medium to another at an angle. Refraction of light is the most commonly observed phenomenon, but any type of wave can refract when it interacts with a medium
Refraction comes into play in many aspects of daily life. Movies and television are made possible by the invention of the lens, a device that relies upon the refraction of light.
The extent of bending of light in a medium is known as REFRACTIVE INDEX
Refractive index = Speed of light in vacuum
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Speed of light in a medium
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REFRACTION EXPERIMENT LAB METHOD
To study this phenomenon, a glass slab experiment is performed and a linear diagram of refraction of light through glass slab is obtained.
Reference : http://www.tutorvista.com/science/linear-diagram-of-refraction-of-light-through-glass-slab
Experiment to Obtain a Linear Diagram of Refraction of Light through a Glass Slab:-
Take a drawing board and fix on it a plane white sheet of paper. In the middle of the paper keep a glass slab and draw its boundary ABCD with a pencil. As shown in the figure below, towards, the side AB, fix two common pins P and Q, so that the distance between the pins is at least 5 cm.
From the opposite side of the pins, that is from side CD of the glass slab, look through the glass slab for the image of the two pins P and Q. Now towards the side CD, fix two more common pins R and S such that the images of the pins P and Q, and the two pins R and S appear to be in a straight line.
Remove the glass slab and the pins. Mark the positions of the four pins as P, Q, R and S respectively. Join the line PQ and extend it to meet the side AB at M. Join the line RS and extend it to meet the side CD at N. Now draw the line MN. Draw normals EF and GH to the lines AB and CD at points M and N respectively.
Mark arrows on the lines drawn PM, MB and NS to indicate the direction of travelling of light ray through the glass slab.
The diagram obtained is a linear diagram of refraction of light through glass slab.
Explanation of the Linear Diagram of Refraction of Light through Glass Slab:-
- Line PM :- Incident ray
- Point M :- Point of incidence
- Line EF :- Normal at the point of incidence
- Angle PME:- Angle of incidence
- Angle FMN :- Angle of refraction
- Line MN :- Refracted ray
- Point N :- Point of emergence
- Line GH :- Normal at the point of emergence
- Line MS :- Emergent ray
- Angle HMS :- Angle of emergence
Reference : http://www.tutorvista.com/science/linear-diagram-of-refraction-of-light-through-glass-slab
