When white light passes through a glass prism, which one of the following colours undergoes the least deviation?

The correct Answer is Red

Explanation

When white light, which is composed of several colours, passes through a transparent medium like a glass prism, it undergoes dispersion. Dispersion is the phenomenon of splitting of white light into its constituent colours. This occurs because different colours of light travel at different speeds within the medium, leading to different degrees of refraction. The extent of deviation for each colour is inversely proportional to its wavelength.

Statement-wise Analysis

The question asks which colour undergoes the least deviation when white light passes through a glass prism. Violet Incorrect. Violet light has the shortest wavelength among the visible spectrum. Due to its shorter wavelength, it travels slowest in the prism and therefore deviates the most. Blue Incorrect. Blue light has a shorter wavelength than green, yellow, orange, and red light. It deviates more than these colours but less than violet. Green Incorrect. Green light has a medium wavelength within the visible spectrum. It deviates less than violet and blue but more than yellow, orange, and red. Red Correct. Red light has the longest wavelength among the visible spectrum. Due to its longer wavelength, it travels fastest in the prism and therefore deviates the least.

Key Takeaway

Red light, having the longest wavelength in the visible spectrum, undergoes the least deviation when white light passes through a glass prism.