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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.

1. 2 sin A
2. 2 cos A
3. 1/2 cos A
4. tan A

Correct answer: tan A

Solution

The refractive index determines the extent of bending of light. Since the refractive index is highest for blue light, it will bend the most, followed by green and red. The critical angle and the relationship with the tangent function are key to solving this problem.

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