Question 132: Ray Optics

Question

Three rays of light, namely red (R), green (G) and blue (B) are incident on the face PQ of a right angled prism PQR as shown in the figure.
The refractive indices of the material of the prism for red, green and blue wavelength are 1.27, 1.42 and 1.49 respectively. The colour of the ray(s) emerging out of the face PR is :

Accepted Answer

At point P,
$$\mu \sin 45^\circ  = 1\sin r$$
$$ \Rightarrow \sin r = {\mu  \over {\sqrt 2 }}$$
For light to come out of prism
sin r should be less than 1.
$$ 	herefore $$ $$\sin r < 1$$
$$ \Rightarrow {\mu  \over {\sqrt 2 }} < 1$$
$$ \Rightarrow \mu  < \sqrt 2 $$
$$ \Rightarrow \mu  < 1.414$$
$$ 	herefore $$ The material which have refractive index less than 1.414, that material can emerge light out of the prism.
Here only red material have refractive index less than 1.414.
$$ 	herefore $$ Red light will come out of the prism.

Answer

green

Answer

blue and green

Answer

blue

Answer

red

Ray Optics

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