Definition of Refraction of light | Important terms Related to Refraction | Cause of Refraction :

Definition of Refraction of light :

The change in direction of light when it passes from one medium to another obliquely is called refraction of light . In other words , the bending of light when it goes from one medium to another obliquely is called Refraction of light.

Important terms Related to Refraction:

1. The plane surface that refracts light is known as the surface of refraction. PQ is the Surface of refraction.
2. Point of incidence: The point on the surface of refraction , where the ray of light is incident is known as the point of incidence . "O" is the point of incidence.
3. Incident Ray : The ray of light which strikes the surface of refraction at the point of incidence , is known as the incident Ray . AO is the incident Ray.
4. Refracted ray : The ray which travels from the point of incidence to other medium is known as the refracted ray. OB is the refracted ray.
5. Normal : Perpendicular drawn on the surface of refraction at the point of incidence is called normal. NON' is the normal on the surface PQ.
6. Angle of incidence: The angle between the incident Ray and the normal at the point of incidence is known as the angle of incidence. Angle of incidence is represented by the symbol i. Angle AON is the angle of incidence.
7. Angle of Reflection: The angle between the refracted ray and the normal at the point of incidence is known as the angle of refraction. It is represented by symbol r. BON is the angle of refraction.
8. In refraction of light , the angle of refraction is usually not equal to the angle of incidence.
9. Refraction of light takes place at the boundary between the two media.

Cause of Refraction:

1. The Refraction of light is due to the change in the speed of light on going from one medium to another.
2. The speed of light is different in different medium , in vaccum or air the speed of light is 3×10`8 m/sec.
3. Greater the difference in the speeds of light in the two media , greater will be the amount of refraction ( or bending ) of light.
4. When the light move from air (rarer medium) into glass (Denser medium) , their speed decrease and their wavelength also decrease.
5. When the light come out from glass (Denser medium) into air (Rarer medium) , their speed increase and their wavelength also increases.
6. Due to Refraction there is a change in both wavelength and speed of light , but the frequency of the refracted ray remains unchanged.
7. The intensity of the incident Ray is more than that of the refracted ray.This is because there is partial reflection and partial absorption of light at the interface.