InterviewSolution
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InterviewSolution
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A beam of light, consisting of red, green and blue colours, is incident on a right-angled prism, as shown. The refractive indices 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 (a) separate part of the red colour from the green and blue colours (b) separate part of the blue colour from the red and green colours (c) separate all the three colours from one another (d) not separate even partially any colour from the other two colours |
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Answer» Correct Answer is: (a) The angle of incidence of all the rays is 45° at the hypotenuse. For a critical angle of 45°, the refractive index must be (sin 45°) -1 = √2 = 1.414. For red light, μ = 1.39 < 1.414. Hence, its critical angle is > 45°. Therefore, red light will pass through the surface into air. For green and blue lights, μ > 1.414. Hence, their critical angles are < 45°. They will be reflected internally and emerge from the surface at the bottom. |
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