8.2.2 Energy and Momentum of Electromagnetic Waves

8.2.2 of Griffith's Introduction to Electrodynamics 2nd Ed
Calculating the energy and momentum of EM waves is not hard. Also, I introduce intensity as it relates to the averages of the energy and momentum.
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[@Daetelus]

I'm trying to understand why in 1900 (before Einstein's 1905 paper) Poincare came up with the same energy-momentum relation that you present here, and I'm not understanding why the momentum doesn't equal 2E/c when energy is defined as (1/2)mv^2 and momentum is defined as mv. Would you be able to shed some light on this for me? I'm no expert on electromagnetism, I haven't watched any of your other videos yet, and my math skills only go up to intro Calc, but I was able to follow this video quite easily.

[@OswaldChisala]

Good show. :)

[@HitAndMissLab]

would it be possible do work out an example? particularly with momentum. As well, does a momentum depend on a wavelength of light?

[@jg394]

RE example: At this level of physics and math, plug-and-chug doesn't really increase understanding. It's better to see how the values change vs. some other change. Perhaps that's what I'll do if I ever do a second version. RE momentum: It varies based on time, position, etc... Higher frequency means it changes much faster.

[@shanmisyntem540]

what is small del ?

[@merikavtelishvili9444]

Is not the first derived formula for u, energy density rather than simply energy?

[@jg394]

Yes, U is energy density = Energy per unit volume, not total energy.

[@sheunveil]

Thank you

[@shreyasoni6490]

I can't understood after B= E÷C 😔

[@sunnypala7629]

Thanks jonathan from india 😃

[@shanmisyntem540]

How did you get epsilon naught time c?

[@chiragkikani7046]

Thankyou

[@ayushijha89]

Discuss the phenomenon of double refraction in uniaxial and biaxial crystal plz solve this question

[@russelas8373]

Why there are lot of indians in comment section....😅

[@economist7758]

Samjh to kuch nhn aata, just bakwas kr raha hy

[@delcydelcy4696]

Thank you