Why do waves bend around objects or when passing through slits? Why does diffraction occur?
Timestamps:
00:00 - Intro
01:13 - What is Diffraction?
02:56 - Huygens' Wavelets Model for the Motion of Waves
04:29 - Wave Interference
07:37 - How Huygens' Model Works (and Explains Diffraction!)
11:24 - Problems with Huygens' Model
12:04 - How Fresnel Modified Huygens' Model (Huygens-Fresnel Principle)
14:36 - Announcement!
Hey guys, I'm back with another video, one which has been requested by a few of you! In this video I discuss a way in which you can VISUALISE how diffraction occurs. Hopefully after watching this video, you'll be able to understand why waves behave in such a strange way when passing through slits or when passing around objects, rather than just accepting that they do.
Of course, I need to make a disclaimer that the scientific models I discuss in this video (Huygens' Wavelets and the Huygens-Fresnel Principle) aren't necessarily how waves actually behave in real life - they're just really good mathematical models that accurately predict how waves behave in real life. But then, that's true of the majority of physics anyway.
Christiaan Huygens came up with a fairly simple but very clever way of understanding wave behaviour by breaking up waves into lots of small chunks that all behave in a very predictable way - by emitting lots of "secondary" waves. His model helped scientists to understand and visualise that waves must indeed bend in a very specific way when passing through a slit, or around an object. The idea that each point along a wave acts as a source of secondary waves, along with the idea that each of these secondary waves interferes with each other secondary wave it interacts with, accounted for a large chunk of observed wave behaviour.
For this reason, I wanted to show you Huygens' model, as well as talk about wave interference. For those of you who don't know about interference, and aren't happy with the pretty speedy and simplistic explanation I gave in this video, I highly suggest you check out the wikipedia page on interference. It's an idea often taught at high school (or college) level physics and it's mega interesting.
Huygens' model, genius though it was, had a few flaws. When we say flaws, what we really mean is that the model's predictions did not perfectly match what we observe in real life. So Jean-Augustin Fresnel came along and modified the model to make sure its predictions did match observed phenomena. Fresnel added an "obliquity factor" to the secondary waves emitted by each point, a sort of attenuation or "strength" factor depending on which direction these secondary waves were travelling in, as well as modifying the phases of the waves moving in each direction from a point source. These modifications to Huygens' original model naturally meant that Fresnel had created a new model entirely. This model is known as the Huygens-Fresnel Principle.
With all of that being said, I hope you enjoyed this video. Please leave a thumbs up and subscribe to this channel if you enjoy physics content like this, as well as to my new second channel Parth G's Shenanigans (link: / @_parthmusic ) if you want to hear some of my music. Also follow me on Instagram @parthvlogs. I'll see you soon!