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# Tag Archives: internal reflection

## Refraction through Prism – A Question

A light ray falls perpendicular to one of the faces of a glass prism of angle 60 and refractive index 1.5,
Find;
a) the angle of emergence.
b) the angle of deviation.
The question implies that the angle of incidence is 0
The ray will enter without any deviation. Therefore, the angle of incidence at the second face inside the prism = 60 degree
(From A +90+ (90-r2)=180)
Since the critical angle for glass is less than this, the ray of light will undergo total internal reflection. So it reflects towards the base internally.

## Why does a test tube seem silvery when put in water?

Why does a test tube seem silvery when put in water?

This is due to Total Internal Reflection. When an empty test tube is inserted in water, the light trying to enter the test tube undergoes total internal reflection and shines like silver.

The air bubbles trapped in a glass paper weight a;lso shines like silver due to TIR.

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