Doubts from "light as wave" Hi all I am a undergrad and in a week or so i || be performing basic solid state and optics experiments. I want u to clear my following doubts. 1. when we say that a light-wave can be written as A(x,y,z) exp(ikxx + kyy + kzz). What does it mean? I mean to ask what kx,y,z represent. Do they represent the angle with some plane at which it is propagating( if yes , which plane? ) 2. When we say " spatial frequency mode of a light" what do we mean 3. How can i imagine Brilloiun zone wrt real space? What are the high symmetry points of a brilloiun zone and how it can be converted to irreducible brilloiun zone( eg ..1st brilloiun zone). 4. What is bragg reflection. How in a periodic medium it do not allow some spatial frequency modes to propagate through the medium?