THIN FILM INTERFERENCE

*Constructive: 2t = (m +
1/2)(λ/n) in one special case!*

*Destructive: 2t = m (λ/n)
in one special case!*

Here *m* is any positive
integer.
These equations are for the
case that n_{film} is greater than n_{air}.
Instead of “remembering a formula,” which will be inappropriate
half the time, it is vital to work out the path and phase
differences from scratch in each individual example.