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A beam of light consisting of red, green and blue colours is incident on a right angled prism. The refractive index of the material of the prism for the above red, green and blue wavelengths are 1.39, 1.44 and 1.47, respectively.
The prism will:
The prism will:
A
separate the red colour part from the green and blue colours
B
separate the blue colour part from the red and green colours
C
separate all the three colours from one another
D
not separate the three colours at all
Detailed Solution
Light falls on the hypotenuse face at $45^\circ$. Total internal reflection needs $\mu \ge \frac{1}{\sin45^\circ} = \sqrt2 \approx 1.414$.
$\mu_{green} = 1.44$ and $\mu_{blue} = 1.47$ exceed 1.414, so green and blue are totally internally reflected.
$\mu_{red} = 1.39 < 1.414$, so red is refracted out — the prism separates red from green and blue.
$\mu_{green} = 1.44$ and $\mu_{blue} = 1.47$ exceed 1.414, so green and blue are totally internally reflected.
$\mu_{red} = 1.39 < 1.414$, so red is refracted out — the prism separates red from green and blue.