Strongly recommended
AT&T Archives: Similiarities of Wave Behavior (Bonus Edition)
Why people recommend it
A vintage Bell Labs film using a mechanical wave machine to show reflections, standing waves and impedance mismatch, often linked to make transmission line concepts intuitive.
Watch for: Good first stop before antenna or signal integrity topics
In their words
And there's similar question to this one, and in an answer, a link to this film from Bell Labs showing a very interesting wave demonstrator.
gbarry on electronics.stackexchange.com, Jan 2017. CC BY-SA.
Like this famous video from Bell Labs, where Dr. J.N.
Rolf Ostergaard on electronics.stackexchange.com, Sept 2014. CC BY-SA.
There is a great old video that demonstrates this principle using mechanical waves, though its the same with electrical waves, you can see the video here (you should really watch the whole thing but I am linked to the exact part of the video where they discuss what I just mentioned).
Jeffrey Phillips Freeman on electronics.stackexchange.com, Sept 2020. CC BY-SA.
