Why Is Huygens Construction Not Used for Double Slit Diffraction?

[SimonB]

A conceptual problem for me anyway!

In the standard texts a Huygens construction is used to explain the diffraction pattern from a single slit. However it is not used in the explanations for double (or multiple slits). What is the justification for this ... the double slit pattern should be two single slit patterns interfering but is that just over complicating things?

Thanks in advance

Simon

 

[SimonB]

I think I have now answered this (?) :

http://www.physics.rutgers.edu/ugrad/labs/1lw.html