# Total Internal Reflection and Critical angle

Physics

## result

### Experimental verifications of total internal reflection

Experiment 1:
• Take a glass beaker with clear water in it.
• Stir the water a few times with a piece of soap, so that it becomes a little turbid.
• Take a laser pointer and shine its beam through the turbid water.
• You will find that the path of the beam inside the water shines brightly.
• Shine the beam from below the beaker such that it strikes at the upper water surface at the other end.
• It undergoes partial reflection and partial refraction.
• Now direct the laser beam from one side of the beaker such that it strikes the upper surface of water more obliquely.
• Adjust the direction of laser beam until you find the angle for which the refraction above the water surface is totally absent.
• The beam is totally reflected back to water. This is called as total internal reflection.

Experiment 2:
• Pour the turbid water in a long test tube.
• Shine the laser light from top.
• Adjust the direction of the laser beam such that it is totally internally reflected every time it strikes the walls of the tube.
• This demonstrates total internal reflection.

## definition

### Critical angle

When the angle of incidence in water reaches a certain critical value, the refracted ray lies along the boundary, having an angle of refraction of 90-degrees. This angle of incidence is known as the critical angle; it is the largest angle of incidence for which refraction can still occur. For any angle of incidence greater than the critical angle, light will undergo total internal reflection.

Definition:
The angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected.

## definition

### Total internal reflection (TIR)

Introduction:
When light travels from an optically denser medium to a rarer medium at the interface, it is partly reflected back into the same medium and partly refracted to the second medium. This reflection is called the internal reflection.

Definition:

Total internal reflection is defined as the complete reflection of a light ray at the boundary of two media, when the ray is in the medium with greater refractive index.