Understanding White Light Separation by a Prism

When a ray of white light passes through a prism, it undergoes a fascinating phenomenon. Instead of simply bending, the white light splits up into its constituent colours. This splitting of white light is what creates a spectrum, similar to a rainbow.

Let's look at the given options to understand which term describes this phenomenon:

• Reflection of light: Reflection is the bouncing back of light when it strikes a surface. This is not what happens when light passes through a prism and splits into colours.
• Refraction of light: Refraction is the bending of light as it passes from one medium to another (like from air to glass, or glass to air). Light does refract when entering and leaving a prism, which causes it to bend. However, refraction itself is just the bending, not the splitting into colours. While refraction is necessary for the splitting to happen, the splitting itself is a distinct phenomenon.
• Dispersion of light: Dispersion is defined as the phenomenon of splitting of a ray of white light into its constituent colours when it passes through a transparent medium like a glass prism. This happens because the refractive index of the prism material is different for different wavelengths (colours) of light. Violet light has the shortest wavelength and bends the most, while red light has the longest wavelength and bends the least. This difference in bending angles causes the colours to separate.
• Diffraction of light: Diffraction is the bending of light waves as they pass around the edges of an obstacle or through narrow openings. This phenomenon is related to the wave nature of light but is not what causes white light to split into colours when passing through a prism.

Based on the definitions, the phenomenon where a ray of white light separates into its constituent colours when passing through a prism is called dispersion of light.

The sequence of colours observed is typically remembered by the acronym VIBGYOR, representing Violet, Indigo, Blue, Green, Yellow, Orange, and Red, in order of increasing wavelength and decreasing deviation (bending) by the prism.