Help with single slit diffraction (fraunhoffer)

[j-lee00]

urgent Help with single slit diffraction (fraunhoffer)

why is it a minimum at a*sin ($$\theta$$) = m*$$\lambda$$,

a = slit separation I would have thought if the path difference is equal to a whole wavelength then there would be constructive interference??

See http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

 

[Doc Al]

Don't confuse the double slit interference condition (http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/slits.html#c1").

In the single slit condition, when the light from opposite ends of the slit have a full wavelength phase difference, that means that half the light from the slit is exactly one half wavelength out of phase with the other half. Which mean destructive interference.