Minimum Deviation
The minimum value of deviation angle achieved when light passes symmetrically through a triangular prism.
Governing formula
n = sin[(A + δ_m)/2] / sin(A/2)
SI unit
Degrees (°)
In depth
At minimum deviation $Δ_m$, the ray passes horizontally inside an isosceles prism ($i_1 = i_2$). Provides an extremely accurate method for measuring refractive index $n$.
Examples in the real world
Using a spectrometer prism table at minimum deviation to determine the refractive index of unknown liquid prisms.