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A ray of light travelling through rarer medium is incident at very small angle i on a glass slab and after refraction, its velocity is reduced by 20%. The angle of deviation  is

Answer:

Explanation:

According to question , at glass-air interface velocity is reduced by 20% of the velocity of light

So, deviation $\delta$ =20% of i

 =  $\frac{20\times i}{100}=\frac{i}{5}$