Chapter 29, Problem 26A

To determine

To Explain: Critical angle in terms of refraction and total internal reflection.

Explanation of Solution

Introduction: 

The angle of incidence that provides an angle of refraction that is is known as a critical angle. The complete reflection of the light ray within the medium such as water or glass from the surrounding surfaces and back to the same medium is known as total internal reflection.

Explanation: 

The critical angle is an angle of incidence at which the refracted ray makes angle perpendicular to the surface.  When a light ray obeys the normal rules for the reflection then the angle of reflection of equal to the critical angle.

The total internal reflection takes place when the angle made by refracted ray is greater than or equal to critical angle. 

Conclusion: 

The critical angle is an angle of incidence at which the refracted ray makes perpendicular to normal of surface.