Question

A prism $ABC$ (with $BC$ as base) is placed in different orientations. A narrow beam of white light is incident on the prism. In which of the following cases, after dispersion, the third color from the top corresponds to the color of the sky?

A.

B.

C.

Answer 1

Use VIBGYOR to arrange the colors of white light in a sequence and then observe which of the diagrams show the color of sky at the said location.

Complete step by step answer: When white light is passed through a prism, it splits into its spectrum of colors. The color spectrum is famously given by the word VIBGYOR, which is short for VIOLET, INDIGO, GREEN, YELLOW, ORANGE, RED. This sequence of spectrum is arranged in terms of increasing order of wavelength. VIOLET being the one with the least wavelength and RED being the one with the highest wavelength.
We know that the color of the sky is blue. If prism is kept with BC in the bottom, the band of color shows violet at bottom and red at top.
So, if we keep BC base, of the prism in the top then followed by indigo and blue.
Therefore, from the above explanation, the correct answer is, option (B)

Note: We need to understand in this question that the first color of dispersion, that is VIOLET is always towards the sharp end of the prism. Separation of light into different colors due to difference of wavelength, when the light passes through prism is called dispersion.