Consider the first order maximum. This happens at the angle where the waves from one slit line up with waves from the next slit that are exactly one wavelength behind.

Call the angle between the first order maximum and the incoming light, theta. The angle between *d* and the incident of light is the same theta but of an imaginary triangle, *d* is the slit spacing (hypoteneuse), and the path difference is landa (opposite).

So for the first maximum, sin(theta) = opposite / hypoteneuse = landa / *d*, so *d* x sin(theta) = landa

So the other maxima occur when the path difference is 2landa, 3landa, 4landa, etc. So the nth order maximum occurs when the path difference is n x landa.

So to make the equation general, just replace landa with n x landa, where n is an integer - the order of the maximum (the order number): *d* x sin(theta) = n x landa

## Comments

No comments have yet been made