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A light ray is incident perpendicular to one face of a 90° prism and is totally internally reflected at the glass-air interface. If the angle of reflection is 45°, we conclude that the refractive index n 

Option: 1

n<\frac{1}{2}


Option: 2

n>\sqrt 2


Option: 3

n>\frac{1}{\sqrt2}


Option: 4

n<\sqrt 2


Answers (1)

best_answer

Total internal reflection occurs in a denser medium when light is incident at surface of separation at angle exceeding critical angle of the medium.

Angle of incidence i>C,  for total internal reflection.

\begin{aligned} &\theta_{\text {cric}}=\sin ^{-1}\left(\frac{1}{n}\right)\\ &45^{\circ}>\theta\\ &\sin \left(45^{\circ}\right)>\frac{1}{n}\\ &\Rightarrow n>\sqrt{2} \end{aligned}

 

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Divya Prakash Singh

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