When light ray enters from one medium to the other medium, it changes its direction in the second medium depending upon the angle of incidence because of the change in speed.
When the light ray enters from denser medium to the rare medium, it bends away from the normal. Its speed and wavelength increases but frequency remains same. Direction of refracted wave depends upon the direction of incident wave.
When light ray enters from rare medium to the denser medium, it bends towards the normal. Its speed and wavelength decreases but frequency remains same.
Direction of refracted ray of light depends upon the direction of incident ray of light.
Law of refraction:
When light ray refracts, it obeys the law of refraction which is as under.
1-Sine of Angle of incidence is directly proportional to the Sine of Angle of refraction.
2- Incident ray, refracted ray and normal all they lie in the same plane.
Important to note:
1- Angle of incidence is the angle between incident ray and the normal to the boundary of the first medium
2- Angle of refraction is the angle between the refracted ray and the normal to the boundary of the second medium, in which light ray enters
3- In refraction phenomenon, direction, wavelength and the speed change but frequency remains same.
4- In refraction phenomenon, if angle of incidence is zero (means ray is coming along the normal) then angle of refraction will also be zero and the wave goes straight in the second medium without bending, but speed and wavelength changes depending upon the nature of the second medium in which it is entering.
5- In this syllabus we study three media, glass, water and air. Glass is most dense medium, then water and water which is denser than air. In water we study two regions shallow and deeper, deeper is the rare medium as compare to the shallow region.
6- Ratio of Sin i to the Sin r is always constant for a particular medium, which is called the refractive index.