The splitting of white light into its component colours is called ______.

dispersion

The correct answer is option 4. dispersion.

When white light passes through a medium such as a prism, the different colors of light that make up the white light are bent or refracted by different amounts because they have different wavelengths. This causes them to spread out or disperse, creating a spectrum of colors. This phenomenon is known as dispersion.

Dispersion occurs because the speed of light varies depending on the medium through which it travels and the wavelength of the light. Each color of light corresponds to a specific wavelength, with red light having the longest wavelength and violet light having the shortest.

When white light enters a prism, the light is refracted as it passes through the prism, and the degree of refraction depends on the wavelength of the light. Since each color of light has a different wavelength, they are refracted by different amounts, causing them to spread out and form the spectrum of colors.

Dispersion is also responsible for phenomena such as the formation of rainbows when sunlight passes through water droplets in the atmosphere and the separation of colors in optical instruments like spectrometers.