Why subsidary maximum has lower intensity physically in single-slit diffraction?

[Arup Biswas]

In single slit diffraction the subsidary maximum has lower intensity than of central. Yes mathematically from the intensity equation we can see that. But how physically we can explain that? When the central and the 1st maxima has same activity to produce constructive interference( as in same phase). We neglect the intensity drop due to extra path traversed as they are very close!

 

[Ibix]

When the central and the 1st maxima has same activity to produce constructive interference( as in same phase).

Does it?

 

[Arup Biswas]

@Ibix the rays there interfere constructively depending on their path difference. In case of central path difference is 0 so phase difference also zero. In case of other maxima due to path difference phase difference must be integral multiple of pi so they are in phase! Doesn't it??

 

[Ibix]

the rays there

Which rays?