Mod-01 Lec-12 The Concept of Phonons

[@jamesberry4514]

It's awesome for a world of students that these lectures have been made available.

[@centerice]

I believe the slide at 11:32 contains an error. I think the terms "photons" and "phonons" at the bottom, are switched. It SHOULD read... "...i.e. Discrete values of energy are allowed, and the smallest unit of one quantum of energy of the elastic wave is called, the 'Phonon.' This is analogous to the concept of 'Photons,' the quantum of electromagnetic radiation." Excellent lecture. Thank you for posting it.

[@sabaansari1491]

I am doing my masters in physics from germany. This is the best lecture I have ever listened!

[@gopalarangarajan3173]

+saba ansari OMG! You have swept me by my feet!

[@aqsaayyoub8409]

Saba Ansari mashaa_Allah .

[@aqsaayyoub8409]

Saba Ansari ab tu ap ka master cmplt ho chuka ho ga

[@wanijavaidahmad1124]

Saba Ansari I also wants to do msc in Germany what should I do. I will give u my watsaap no.if u want u can connect with me [phone]

[@md.shahididrishi5720]

from which university

[@PaulGaurav]

The analogies made are extremely helpful in understanding these concepts. Thank you Professor.

[@anushri3257]

Was trying to understand phonons for a thermodynamics course, this lecture made my concepts really clear!

[@christiankook9614]

I love his teachings and his accent, it doesn't get better than this

[@alimo166]

This channel is one of the best scientific channels I have ever used on KZbin.

[@VikasKumar-et5lv]

Sir @11:29 the slide describing the concepts of phonons, there is a mistake that phonon is placed in position of photon and vice versa

[@samuelwolnerman7765]

Wasn't sure if i was going crazy or not, so thank you for this

[@BruceWayne-ve9nl]

yaa I also think there is correction needed.

[@ahmedhass146]

Nice lecture professor Nice introduction and nice connection between the concepts

[@designerguy_13anuragsharma59]

Oh thanks i got exactly what i was looking for i.e understanding the non propagating phonon approximation

[@Th3CuriousGeorgE]

this guy knows his stuff and how to teach it

[@abhilipsasarangi6236]

thank u sir lecture is very gud to understand ,again thanks a lot sir.

[@sajidsaikia6320]

In 11.30 min of the lecture, the definition given mentioned "photon" instead of "phonon" and vice-versa (last line)

[@live4Cha]

excellent. i think the specific heat C should also incorporate the fact that it is the amount of energy that a material can take. if we add dQ to the system and assume all is absorbed, a portion of this dQ increases the temperature while another portion goes into internal energy defined by C. this C should be a measure of entropy.

[@bharatheshbadadamath5394]

but defination of specific heat is amount of heat required to rise temperature to 1 degree not internal energy, anyone can clarify me :)

[@عبدالعزيزيونس-ذ9ظ]

Is it possible to vibrat crystal lattes by acoustic wave (phonons) to make photons and vice versa?

[@stephensmith799]

Dear Professor Rangarajan, My physics education ended age 15 and was almost completely Newtonian! I have a question about the passage of phonons through metals and between bodies of different density and mass. The reason I ask is because I have invented a new kind of stringed instrument and I want to know how to maximise the efficiency of the transmission of phonons from one material to another, for example from hardwood to aluminium, or from glass to aluminium. We are trying to design quick-release fastenings between component parts of different density and mass. In the interests of efficient transmission, should the surface area of contact be as large as possible? Converesly can phonos transmit energy as easily from one body to another via small points of contact? And if I may ask another question.... 'Presumably, considered in the light of quantum theory, phonons have different definite and discrete energy values. 'Do phonons of one energy state pass from one material to another more readily (efficiently) than phonons at a different energy state?' (Please excuse the naivity of my questions as my education is in an entirely different field.) My aim is to create a musical instrument with the highest possible inherent ability to sustain musical notes.

[@gopalarangarajan3173]

+Stephen Smith On the face of it, I think the factors of relevance might be more on the macroscopic scale: Let me think over it and get back to you. I am happy to have found some one who has asked me some thing which I cannot answer straightaway!

[@stephensmith799]

+Gopala Rangarajan Thank you. I've let my Chief Designer know we have a Physicist thinking about these questions! ;-)

[@safnasaif2337]

masha Allah! How simply u explain sir !

[@gopalarangarajan3173]

+Safna Saif Salam ale kum! (Dont know if I got it right) Very happy to build a small bridge across the encircling gloom of mistrust. Science is the weapon of real progress. Make love, not war!

[@BruceWayne-ve9nl]

@@gopalarangarajan3173 very well said my friend

[@nazishahmad1337]

@@BruceWayne-ve9nl Bro he's the professor teaching the course Gopala Rangarajan .

[@gayathri.r.pisharody7157]

Sir, In the quantum theory of specific heat, we have considered each atom as a quantum harmonic oscillator having energy of (n+1/2)hvSo when we take the average energy should we substitute "(n+1/2)hv" instead of "nhv"? kindly consider my doubt sir.

[@uditdave7855]

Gayathri.R. Pisharody yes sir why????

[@SumitBanikYT]

The reason behind neglecting the term 1/2hv is to make the averaging easier. If you put (n+1/2)hv instead of nhv the average value would increase by a constant 1/2hv . You can check it yourself, simply substitute. This 1/2hv is the zero point energy at absolute temperature and do not play a role in specific heat as specific heat involves only the derivative of internal energy with temperature and hence the constant term 1/2hv plays no role at all.

[@oldcoder9000]

Very good lecture

[@gopalarangarajan3173]

+oldcoder9000 Thank you for thinking so and saying so. I am grateful.

[@kodaiimman]

wow what a lecture its very nice professor

[@keamolefhe2188]

could u pliz show us how they got to those equations.

[@ДмитрийБурбовский-м8д]

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[@laraibharoon5404]

this is realy a good lectur

[@godfather6595]

Sir why there is no lecture on classical theory of lattice vibration

[@physiatristonline]

sir what about say ultrasound in air...can it be considered a phonone

[@muhammadazizrahman2264]

awesome lecture!

[@videoviewerviewer4107]

Really a very nice lecture

[@kingsukbandyopadhyay9662]

Well explained.

[@laraibharoon5404]

thank you so much Sir i am from Pakistan tomarow is my presentation on einstien model please pray for me☺

[@aqsaayyoub8409]

Laraib Haroon hahahah

[@videoviewerviewer4107]

Nice Lecture

[@videoviewerviewer4107]

Thank You Sir

[@shoubanaliali5794]

Great

[@avral4148]

Great!!!

[@drypickle313]

nice

[@andreblaser5713]

danke thank you

[@gopalarangarajan3173]

+Andre BLASER Bitte sehr! Ich bin freu! (Is that right?

[@BambaMeme]

polyriddim

[@KiranKumari-no4ld]

sir plzz vedios mai hindi language use kre

[@jiangjiangjiang3124]

his english is too difficult to listen

[@laraibharoon5404]

this is realy a good lectur

[@shoubanaliali5794]

Great

[@shoubanaliali5794]

Great