Question

What is critical angle and total internal reflection?

Answer 1

the incident angle at which the refracted ray forms 90° with the normal is critical angle.

when the incident angle is increased more than critical angle, the ray reflects in the same medium, it is called TIR

Answer 2

CRITICAL ANGLE -WHEN A RAY OF LIGHT PASSES FROM A MEDIUM OF HIGHER OPTICAL DENSITY TO A MEDIUM OF LOWER OPTICAL DENSITY ,THE ANGLE OF INCIDENCE AT WHICH THE ANGLE OF REFRACTION BECOMES 90° IS THE CRITICAL ANGLE.

TOTAL INTERNAL REFLECTION-WHEN A RAY OF LIGHT PASSES FROM A MEDIUM OF HIGHER OPTICAL DENSITY TO A MEDIUM OF LOWER OPTICAL DENSITY AT AN ANGLE OF INCIDENCE GREATER THAN THE CRITICAL ANGLE,THE RAY IS REFLECTED BACK TO THE SAME MEDIUM WITH OUT UNDERGOING REFRACTION.THIS KNOWN AS TOTAL INTERNAL REFLECTION.