10. Traveling Waves

[@RudradeepMukherjee]

The demonstration of traveling waves through two different media was so cool. Thank you for the effort, professor. Thank you, OCW.

[@akaikeshi1906]

If I had real professors like Mr Lee you'd never catch me playing hearthstone during class 😭

[@MM-vw1ck]

42:01 My man playing hearthstone midclass

[@jonahansen]

I wish (in the derivation of the reflected and transmitted waves) that Prof Lee had stuck to the argument convention kx-wt for right traveling and kx+wt for left traveling waves as he spent so much time explaining in the first part of the lecture. It probably works out OK the way he did it, but it makes me want to derive it with that argument set - probably a good exercise for the viewer, eh? Anyone else have thoughts on this?

[@forfun5140]

1:01:49 Can someone please explain how the integration pulls out 1/ω?

[@wintg931]

chain rule: df(omega * t)/dt = omega * df'(omega * t)

[@eamon_concannon]

36:02 Can you please explain why you use T instead of 2T for the stretching force on the string element when calculating its potential energy. Doesn't a force T act on both ends of the element?

[@iliasp4275]

I think (not sure) it is because we want to mesure the W of the force that we are applying, which is equal to T, on the one side of the string. The other T is the reaction of the string which is equal to the force that we put, but we dont care about it's W. We only want to mesure the energy that we are giving the system. I think about pulling the string once and then letting go. The moment you let go there will only be on T going down, which is actually the Potential Energy that is stored in the string, Which is the same as the force that we applied * the distance we streched the string

[@DevSingh-ub8bn]

what is answer of this question

[@bbeeyangli]

Perhaps it's because according to his diagram, the point on the left is fixed, resulting in a displacement (ds) of zero, and therefore no work is done. As for why the left side is fixed, it was not explained. This is a common issue, as many courses from MIT and other universities or individuals often have inaccuracies and ambiguities, including MIT's math courses. Courses that are extremely detailed and precise are very rare. In fact, he should have taken any small segment of the waveform, and the work done is the sum of both sides, Tds1 +Tds2 (all ds>0) , which together amounts to Tds(ds=ds1+ds2), as if one end is fixed, and all displacements are considered as combined on one side. This perspective suggests. (Ignoring these shortcomings, many courses are still very interesting and great. By the way, this MIT course on waves is also quite fascinating! Another flaw of the course is that the mathematical part should directly use a mathematical framework, such as ordinary differential equations, and transform them into algebraic equations using mathematics directly, without the need to first set up exponents and then derive. Also, the part on eigenvalues did not address related issues of degeneracy and the completeness of the basis of vector spaces.)

[@DevSingh-ub8bn]

@@bbeeyangli not satified with your answer but thanks for sharing your idea..

[@heiheihei60]

someone is playing hearthstone at the back lol 27:40

[@fatiheneskose4477]

Before i watch the video, i supposed these things are being done only in my country :)

[@zanisxeroxhou9900]

And at 41:03

[@fruitea8907]

Bro's been playing the whole lecture🤣

[@ayushwithasingle_a]

2:40 LOL!!

[@alexcaruso6420]

50:11-50:45 PDA LOL

[@ayushwithasingle_a]

what is R and †(tao) at the end? What does it mean?

[@Nisargp100]

Seems like R = the fraction of initial pulse\wave refracted at a boundary and Tau = fraction of initial pulse\wave transmitted across a boundary.