Line of Polarizers Reflection Question

[Coolcrab]

http://plc.cwru.edu/tutorial/enhanced/files/lc/phase/Graphics%5Cschem.BMP
I was hoping someone could help me with understanding why a row of polarizes reflects a light wave when the whole row (the pitch P) is the same length as the wavelength of the light.

[PLAIN]http://www.aetherwavetheory.info/images/physics/color/cholecteric_color.gif[PLAIN]http://www.battlesnake.co.uk/_uni/lcd_files/image006.gif

I prettymuch get the physics behind the rest, just don't understand this little part. Why only the light of that length and does this also apply for light coming in at a different phase than the crystals?

 

[Coolcrab]

So I've been reading my optics book (again) and came on an insight, could it be because all the reflected red light is in the same phase and has constructive interference while all the other light has destructive interference?