11.5 CHAPTER 11. 2D AND3D WAVEFRONTS
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��������The picture above shows how the waves add together to form the interference pattern.
The peaks correspond to places where the waves are adding most intensely and the
minima are places where destructive interference is taking place. When looking at
interference patterns from light the spectrum looks like:
There is a formula we can use to determine where the peaks and minima are in the
interference spectrum.There will be more than one minimum. Thereare the same
number of minima on either side of the centralpeak and the distancesfrom the first
one on each side are thesame to the peak. The distances to the peak fromthe second
minimum on each sideis also the same, in factthe two sides are mirrorimages of each
other. We label the firstminimum that corresponds to a positive angle from the centre
as m = 1 and the first on the other side (a negative anglefrom the centre) as m =− 1 ,
the second set of minima are labelled m = 2 and m =− 2 etc.