When a point source of light is far away

Shift the system of three slits further and closer from the point light source. Observe the position of the beams. What do you notice?

Why we are studying this

Even very distant and enormously large light sources are like point sources to an observer on the ground. We will try to understand why the light reaching us from stars is like a parallel bundle of rays.

How we study it

Put together the diagram below. Change the distance between the slits and the light source and see how the image of the rays behind the slits changes.

What we can conclude from this experiment

If we select some rays to study from the light of a point source, the angle between these rays near the point source is large. However, as we move away from the point source, this angle decreases. We can imagine that moving further away, these rays are almost parallel.