Prism and deviation
Intermediate
A prism bends light and disperses colours.
n = sin((A+δ)/2)/sin(A/2)A prism deviates light twice and disperses colours. n = sin((A + δ_min)/2)/sin(A/2) at minimum deviation.
A = 60°, δ_min = 37°: n = 1.5.
Violet bends the most.
In more detail
A prism refracts light twice, once at each face, and deviates it by an angle depending on the prism angle and refractive index. Minimum deviation occurs when the ray passes symmetrically through the prism.
Real-world uses
- Spectrometers use prisms to measure refractive index.
- Binoculars and cameras use prisms to redirect light.
- Spectrometers use a glass prism to split light into colours, which helps identify elements by their spectral lines.
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Frequently asked questions
What is minimum deviation?
The smallest deviation the prism can produce, which occurs for symmetric passage.
Does the deviation depend on colour?
Yes, the refractive index varies with wavelength, so different colours deviate differently.
Why does a prism deviate light?
Light bends at each face, and the total deviation depends on the refractive index and the prism angle.
Related topics in Optics
Critical angle · Total internal reflection · Applications of TIR · Dispersion · Rainbow formation · Scattering of light