**1. The problem statement, all variables and given/known data**

Is it necessary that a single slit diffraction occur with the two source having the distance of [itex]\frac{a}{2}[/itex]?Are there any diffractions occur when the point source having the distance of [itex]\frac{a}{3}[/itex],[itex]\frac{a}{4}[/itex] and so on?

And I would like to know whether are there only destructive interference occur?

**2. Relevant equations**

**3. The attempt at a solution**

http://ift.tt/1cVBtU1