Why does a wave entering a slit form point sources in Huygens' principle?

[Toby_Obie]

Hello , as per diagram (attached) regarding Huygens slit experiment / diagram

When the wave enters the slit - why does it form a number of point sources ?

There are 6 as per the diagram, Are these the horizontal wavelengths of the electromagnetic waves ?

Thanks, much appreciated

 

[ideasrule]

The "why" part is pretty easy to understand intuitively if you think about waves on a pond. These waves are created when something disturbs the water's surface--that is, something moves the water up or down. A wave moves water up and down, so the wave itself creates waves that spread out in all directions. In other words, every point inside the wavefront is creating new waves.

6 was as arbitrarily chosen number. In reality, every point in the slit sends out a wave.