L:  Distance between the slit and screen (m)

Xm:  Distance from the central maximum to the mth maximum

λ:  Wave length (m)

m:  Order number (whole number, 1, 2, 3)

d:  Distance between the slits (m)



m. λ = d.sin θm   (for maxima)


m. λ =   (for maxima)


sin θm =   (for maxima)

For minima (nodal lines), use  .λ


For mixama, use (m. λ)


x::  Spacing between two maxima (or two minima).  It is constant.


λ = d.∆x / L


1m = 109 nm