Physics – 3.2.2 Refraction of light | e-Consult

Demonstrating Dispersion with a Prism: When white light passes through a prism, it is dispersed into its constituent colours (the spectrum). This occurs because different colours of light have different wavelengths, and the refractive index of the prism material is slightly different for each wavelength.

Path of Light and Colour Separation: White light enters the prism and refracts. The amount of refraction depends on the wavelength of the light. Shorter wavelengths (violet/blue) are refracted more than longer wavelengths (red). This difference in refraction causes the different colours to separate as they travel through the prism. The violet light is bent the most, and the red light is bent the least. As the light exits the prism, it refracts again, further separating the colours.

Factors Affecting Dispersion: Several factors affect the amount of dispersion observed:

• Prism Material: The material of the prism significantly affects dispersion. Different materials have different refractive indices, and the dispersion properties (how much the refractive index varies with wavelength) are different for each material. Glass is commonly used because it has a moderate dispersion.
• Wavelength of Light: Dispersion is wavelength-dependent. The greater the difference in refractive index between the prism material and the wavelength of light, the greater the dispersion.
• Angle of Incidence: The angle at which the light enters the prism can also affect the amount of dispersion. The dispersion is generally more pronounced at certain angles of incidence.