NCERT Class 10 Science — Chapter 2: The Human Eye and the Colourful World

The correct Answer is

A beam of white light

Explanation

The phenomenon described involves the dispersion of light through a prism and its subsequent recombination. This principle demonstrates that white light is composed of various colors, which can be separated and then recombined to form white light again.

Statement-wise Analysis

The question describes an experiment where a second identical prism is placed in an inverted position with respect to the first prism in the path of a dispersed spectrum. 1. When white light passes through the first prism, it disperses into its constituent colors (spectrum) due to different refractive indices for different wavelengths. Violet light deviates the most, and red light deviates the least. 2. When this dispersed spectrum then passes through a second identical prism placed in an inverted position, the second prism effectively reverses the dispersion caused by the first prism. 3. The different colors of light, which were separated by the first prism, are now refracted in such a way by the inverted second prism that they recombine. 4. This recombination results in the emergence of a beam of white light, parallel to the incident white light beam, from the second prism. This experiment was famously demonstrated by Isaac Newton. Therefore, the result is a beam of white light.

Key Takeaway

An inverted second prism can recombine the dispersed spectrum from a first prism back into white light.