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Optics
Optics

Double-Slit Interference

dsin⁡θ=mλd\sin\theta = m\lambda

Condition for constructive interference (bright fringes) in Young's double-slit experiment.

Variables

d
Slit separation
m
\theta
Angle to maximum
°
m
Order number
unitless
\lambda
Wavelength
m

Derivation

Derived from path difference between light from two slits being an integer multiple of wavelength.

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Common questions

What is the Double-Slit Interference formula?

Double-Slit Interference is written dsinθ= mλ. Condition for constructive interference (bright fringes) in Young's double-slit experiment. It belongs to Optics, under Wave Optics.

What are the units in dsinθ= mλ?

In SI units, d is slit separation, measured in m; \theta is angle to maximum, measured in °; m is order number (dimensionless); \lambda is wavelength, measured in m.

How is the Double-Slit Interference formula derived?

Derived from path difference between light from two slits being an integer multiple of wavelength. The result is dsinθ= mλ.