Refraction and refractive index


1) When light falls to an another transparent medium some part of the light gets reflected back to the first medium and another part of the light enters to the second medium.



2) When light enters to the second medium its path of direction changes.


3) This phenomenon of changing light path in the second medium is called refraction.



4) During refraction many situations happens, first the velocity of light changes,  velocity of light in second medium is completely different from the first medium. But one thing is always constant that is






5) This ratio is always constant and called the refractive index of the second medium with respect to the first medium denoted as




 


6) During refraction when incident ray strikes at P position of the second medium, some light reflected back to the original medium 1, as shown in the diagram.



7) Another part gets enters to the second medium but in a different direction that is its direction changes, as shown in the diagram, and it is called refracted light.



8) Now a normal is drawn at the position P, Now



9) refracted light makes an angle r to the normal called refracted angle.