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Optics
Optics

Thin Film Interference

2nt=(m+12)λ2nt = \left(m + \frac{1}{2}\right)\lambda

Condition for constructive interference in thin films (when one reflection has phase shift). For destructive: 2nt = mλ.

Variables

n
Refractive index of film
unitless
t
Film thickness
m
m
Order number
unitless
\lambda
Wavelength in vacuum
m

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Common questions

What is the Thin Film Interference formula?

Thin Film Interference is written 2nt = (m + 1/2)λ. Condition for constructive interference in thin films (when one reflection has phase shift). For destructive: 2nt = mλ. It belongs to Optics, under Wave Optics.

What are the units in 2nt = (m + 1/2)λ?

In SI units, n is refractive index of film (dimensionless); t is film thickness, measured in m; m is order number (dimensionless); \lambda is wavelength in vacuum, measured in m.