Question

Explain the concept of refraction, total internal reflection and critical angle.

Answer 1

1.Refraction :

The change in the direction of propagation of light as it passes obliquely from one transparent medium to another is called refraction of light.

2. Total internal reflection and critical angle:

When light travels obliquely from a denser medium to a rarer medium, the angle of refraction r is greater than the angle of incidence i. Also, the ratio of sin i / sin r is constant. For a particular value of i ,r becomes 90°.This particular angle of incidence is called critical angle. For i > critical angle, as r cannot be greater than 90°,light is totally reflected in the denser medium.This is called Total internal reflection.

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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.

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