What is a Photon?

We round out the nature of light with what exactly a photon is, and other various properties of the electromagnetic spectrum. This is part of my intro Astronomy class taught at Willam Paterson University and CUNY Hunter.

[@PhilDockery]

This was profoundly incredible for me: I have never understood this until now, thanks to the way you explained how the electromagnetic spectrum works. Thank you! New subscriber!

[@JasonKendallAstronomer]

Glad it helped!

[@markwhitt8488]

This was something that I've been curious about for a long time. I've seen clues in a lot of other places, but it didn't really click for me until now. What surprised me the most is that for some reason I had been under the impression that only electrons absorb and emit photons. Realizing that protons do as well is a significant mental shift for me. I already knew that electrons absorbing and emitting a photon will change the electron's energy state. Finding that protons also have similar energy states helps to understand the different types of radiation, as well as helping to make better sense for how neutrons play a different role in all of this. Now I'm curious about how the enormous mass difference between an electron and proton affect the whole process of photon generation - and suddenly, nuclear physics is very interesting! I didn't realize that actually knowing what a photon is would be so revealing. So a really big THANK YOU! Just now finding your channel via this video and it looks like a wonderful treasure trove. Can't wait to dig into more.

[@lepidoptera9337]

Electrons aren't absorbing photons. That is ruled out by conservation laws. Electrons on their own can scatter photons, i.e. there has to be an outgoing photon if there was an incoming one. Only compound systems like atoms and protons can fully absorb photons, even though at the end of the day those are also just scattering processes.

[@IzySly-g4h]

I can tell by the comments that I need some popcorn and a beer because I am going to love this! Thank you for uploading this video.

[@JasonKendallAstronomer]

Rock on!

[@Fat_Tony_Capaldi]

Excellent content my friend. Keep up the good work!

[@danasotornik]

Thank you for explaining what photons are. I finally understand it.

[@JasonKendallAstronomer]

Glad it was helpful!

[@IzySly-g4h]

I am working on a pair of glasses that let you see the double slit experiment and interact with it, can you help me explain to someone what it is that they are actually seeing with the observer effect? Thank you in advance for responding.

[@ONEYEDPiRAT]

Holy cow it's a real person thanks dude!

[@JasonKendallAstronomer]

No AI here...

[@rebanelson607]

I don't think I can live long enough to really understand this stuff but thanks for this excellent presentation!

[@Just.A.T-Rex]

Early Christmas!! Woot woot

[@86congtymienbac80]

The electromagnetic field radiates into space in a spherical shape. Considering a photon when emitted, why is its energy completely absorbed at one point on that sphere? Do other points on the sphere not receive any waves?

[@JasonKendallAstronomer]

Well, it is a quantum of energy. Also, that seems to be a fairly advanced question that'd go deep into Quantum Field Theory. Suffice it to say that we can have electron/photon collisions that transfer momentum, such as Compton Scattering and the Photoelectric Effect. These both provide evidence of the photon acting like a particle. So there would be a wibbly-wobbly-wavey-pointy "contact place" where their wavefunctions would overlap, and scatter off each other. It's all very peculiar at that exact impact point, which really can't be a "point". I recommend hunting down Feynmann's Lectures on the topic.

[@86congtymienbac80]

@@JasonKendallAstronomer Some experimentalists say that the electromagnetic field is the average sum of many photons. This seems to imply that photons act as substantial, directional beings (like "rays of light") and that electromagnetic fields are illusory. So does it make sense to model a photon as a packet of many electromagnetic waves with an average frequency? Here is his explanation: "The classical electromagnetic field is the average of many quanta. It simply doesn't exist for "one photon". How would you measure it, exactly? Do you remember how these quantities were defined in high school? As the forces on charges and currents. No such measurement is possible except in the classical limit."

[@86congtymienbac80]

@@JasonKendallAstronomer If you want to explain light as a kind of classical electromagnetism, I think, describe the growth of waves in space like a balloon. A component such as surface tension is needed so that when energy is absorbed, that electromagnetic wave energy must be concentrated to one point.

[@marklong7698]

So good!

[@stridedeck]

You never explained the mechanical cause of a "charge", only its observation of pushing away and pulling towards. Also, the "field" is not described as to its original formation. Each quantum has its own field and there are 17 fields throughout the universe, but what is the substance of a field and the fabric of space?

[@JasonKendallAstronomer]

I think, for this particular video, that I was aiming not at describing the entire Standard Model, but rather just getting an intuitive feel for how these photon things work. Perhaps someday, I'll hit the SM, but that's not really in the scope of a lecture series that's principally aimed at an introductory astronomy class level. However, thanks for the very good idea about doing just that! It'd be an exciting journey.

[@kellyrobinson1780]

I can help with one of your questions. "Charges" just ARE. They're a fundamental property of protons and electrons. They simply exist. They can't be broken down, or explained, or simplified. They are just a basic property of their respective particles. Just as water is wet. It just IS, and charges just ARE. I hope that's helpful.

[@kenh9508]

Thank you!

[@joeharmon3301]

If “old” light can turn into matter… could that be what dark matter and/or dark energy is??

[@alitlweird]

Photon Torpedoes.

[@phukfone8428]

Luminiferous aether

[@kellyrobinson1780]

So you're a time-traveler from the late 19th century?😁🤙