\[\lambda=\frac{2nt\cos(\theta)}{m}\]
Variables
lambda[λ]wavelength
nrefractive index of film
tfilm thickness
theta[θ]internal angle [rad]
minterference order
Description
What is this formula?
This formula calculates the wavelength associated with constructive interference in a thin film. Interference occurs because light waves reflected from different surfaces travel different optical distances.
When to use it
Use this formula when studying thin-film coatings, soap bubbles, anti-reflective coatings, and optical layer systems.
Example
Given:
n=1.50
t=4×10^-7 m
θ=0 rad
m=2
Formula:
λ=(2ntcos(θ))/m
Substitution:
λ=(2×1.50×4×10^-7×cos(0))/2
Result:
λ=6×10^-7 m
Applications
- Anti-reflective coatings
- Optical filters
- Thin-film sensors
- Surface coatings
- Optical engineering