# White light diffraction

I have a hard time understanding why light waves of different wavelengths diffract in a different manner. According to Huygens' principle, every point on the wavefront is a source of a secondary wave. So if we have a white light going through, say, a single slit (light rays parallel to each other and perpendicular to slit's plane), all what's supposed to happen is a plain diffraction, just like of any other wave. That is, the wave will progress spherically, but it will still be a white light. Why instead we get a splitting of different wavelengths? In other words, how does light color affect diffraction geometrically?

• You should understand that diffraction is not changing the direction of the wave. Diffraction is interference of waves. Depending on the wavelength, the waves will interfere constructively an destructively at different points of space. Commented Jan 23, 2014 at 18:15
• @cinico - though fundamentally they are the same phenomena, diffraction is "cutting off" the wavefront, leaving only part of it which will basically interfere with itself. The problem is that I do not understand why should the interfering process around the edges be different than before hitting the slits. That is, why wouldn't the waves making the white light (superposition of all waves of visible light) continue interfering with each other, just like before with the only exception of being spread out spherically. Commented Jan 23, 2014 at 19:22