A: The light source helps explain both. My latest video will show you, here:
As I promised in a previous post, in this video I also explain the difference between parallel beams and parallel rays:
CONTENTS
00:00 Intro to the Plane Wavefront Generator (PWG)
01:05 Parallel rays vs. parallel beams
06:32 Building the PWG
13:40 Collimating the PWG
15:14 Young’s slits with the PWG and 3D printed ‘slits’
17:24 Köhler’s conjugates
