Correction: In pair annihilation, there should be two photons (for conservation of linear momentum) instead of one.. It skipped my mind while drawing the diagram.
In pair production the recoil nucleus carry some momentum of the photon. The energy of the recoil nucleus is negligible or we have to consider it for calculation?
yes sir. very nicely explained. sir how can we write momentum conservation equation for annihilation? Check this if it is right... initial momentum=final momentum 0 = hf/c+(-hf/c) hf/c=hf/c.
An electron-positron pair can't annihilate into a single photon, for precisely the same reason as a single photon in vacuum can't convert into an electron-positron pair. Such a process wouldn't satisfy the law of conservation of momentum.
Sir If a no. B/w 0 and 1 is multiplied to any no. The result that comes is smaller than the original no. Hence here when you multiply by v/c and cos⁰ you are using a no. Which is b/w 0 and 1 and as you are multiplying it with 2(gamma)m⁰c² then the result that we arrive is hv>2(gamma)m°c² But you have written hv
What a clear explaination ! Hand moves ,eye contact , clear tone and accent everything is so perfect with this man ...can't help falling in love with the way he teaches .
I think I've found THE physics channel in the Indian youtube space, and I have seen them all. Your presentation is very clean, your articulation very precise and these are the two things I found lacking in the others. Great lesson!
Hey sir!! I am going for interview fir TIFR this year that's why I am preparing... I had a lot of confusions related to pair production but now all has been cleared.... So thanks ❤❤❤🙏🙏🙏🙏
8:20 I would say the positron has momentum: p(+) = p . cos(- theta) = - p . cos(theta). So the momentum of the photon (p) should be equal to the difference: p(-) -/- p(+); with p(-) being the momentum of the electron. Then the min-sign vanishes and we get this 8:56. And here 11:04 we should have "a bigger than"-sign (>).
1. Can a free electron absorb a photon? ua-cam.com/video/QRCSlbOhMFU/v-deo.html 2. Can you Prove E=MC² ? ua-cam.com/video/VZEhmWFlrnM/v-deo.html 3. What is a Black Hole? Understanding the first ever image of a Black Hole ua-cam.com/video/WuYpI3EoCnM/v-deo.html
To be honest, sometimes I could not bear with Indian teachers because their accents are too strong and it's hard for me to understand, but this teacher is absolutely amazing. He explained the whole process clearly with beautiful handwriting and intonation. Thank you
Seems that if pair creation only required energy of a certain level, it would occur in ALL conditions that involves high energy, which would include any such high energy photon travelling in vacuum. It simply cannot be a high energy photon on it's own. It MUST impact something. While it's far more likely for the photon to encounter a target in non vacuum environments, that does not logically translate to "cannot happen in vacuum" but rather it is UNLIKELY for a collision to happen in vacuum, but it CAN happen
I'm pretty sure it's clear that the question is about a pure vaccuum, not one where a collision with some particle is possible. And if there's a particle there, then the neighborhood containing that particle isn't a pure vacuum. What you want to say is that photons in space in this universe can impact particles because IRL space is full of particles, just very sparsely populated in some places at some times, therefore we should see particle creation at some rate in any appreciably-sized region of IRL space.
My suggestion is that: 1. the singularity before the Big Bang was all photons, and 2. that the universe was made by pair conversion where photons make electron positron pairs. Readers challenge me with, how can you prove that? Most of it has already been proved! These 3 things that we know are true, support many of my ideas on the importance of photons in physics 1. Photons are outside of time and distance. 2. Photons create an electron positron pair in pair conversion. ( During extreme conditions photons can create proton, anti proton pairs; and neutron, anti neutron pairs). 3. Should all the mass be converted to energy, we would have a universe of photons.
Thank you so much sir..I have few confusion about how nucleus help to conserve energy and momentum. Now it's very clear . This question was asked me in PhD interview at IIT indore but I was unable to explain them clearly and got rejected. Thank you sir for clarity. Please refer me that why we can't measure simultaneously position and momentum conceptually.. 🙏🙏
How you will measure position? You have to draw a position vector but measurement will take some time.and measured value will be different from actual value.larger the speed larger will be the error.hope it works.
Well, you didn't explain the momentum conservation for pair annihilation. I got stuck at that place, where I don't know how to prove simultaneous momentum and energy conservation for pair annihilation.
Sir, it also proves that ..nothing is really needed for destruction of masses(pair annihilation).. but construction or creation(pair production) needs some material!!!..
Hey, sorry for resurrecting an old video. I have a questions though - if annihilation in vacuum is possible, but a pair creation isn't, doesnt this violate the time symmetry? Thanks.
Suggestion: you should make videos on non-interial reference frames and about acceleration in special relativity. Also about dirac's Unification of quantum mechanics with special relativity.
I have a little question that during the pair-production, as the Positron is created from the hole in the negative energy state and also the electron goes to the positive energy state, it doesn't mean that every -ve energy state region can produce this electron-positron pair? I mean to say that from Dirac's theory, he considered vacuum as a sea of negative energy but as you showed pair production can't happen in vacuum, so that means there can be negative energy region but that doesn't mean that pair production can happen there?
Thanks sir best description.we say that proton is a stable particle but As the consequences of Grand unification theory it is an unstable particle so what is this?
Stable means it has a very large half life. It doesn't mean that it is a fundamental particle. Infact a proton is not fundamental. Still it is quite stable, and proton decay has not yet been experimentally observed.
I have a question in my mind if u can clear it sir?? If a photon of energy 1.02Mev creat an electron positron pair then the electron positron pair must be at rest because all of the energy of photon is converted to mass. Now if momentum of the photon is non zero and the momentum of the electron positron pair is zero which means momentum is not consereved. My question is that as all the mementum is used in recoiling of the nuclesus??
Although mass energy equivalence of special relativity allows conversion of a photon to an electron-positron pair, such a process cannot occur in free space because A mass is not conserved B energy is not conserved C momentum is not conserved D charge is not conserved Why
In electron positron annihilation negative and positive charge appearto split among emerging photons. If photon carries partial charge then in pair production how can it produce electron and positron each of which carry full charge.
Its really nice to watch your explanations, sir.. however, isnt it two oppositely directed annihilation photons of energy 511Kev.. (which is the priniple of detection of positrons in PET scan )?
A photon is an elementary particle, a quantum of light (or electromegnetic radiation). It has no electric charge or rest mass. A positron is an elementary particle, an antiparticle of an electron. It has rest mass of about 0.5 MeV, and positive electric charge (same magnitude but opposite sign than an electron). A proton is a composite particle (it consists of quarks). Protons and neutrons are together called nucleons, because they appear in an atomic nucleus. It has rest mass of about 938 MeV (about 1800 times the mass of an electron), and a positive charge of the same magnitude as an electron.
Thanks. But it looks like it is also impossible for the photon without splitting into two directions during annihilation. it will disobey the conservation of momentum as well.
Correction: In pair annihilation, there should be two photons (for conservation of linear momentum) instead of one.. It skipped my mind while drawing the diagram.
In pair production the recoil nucleus carry some momentum of the photon.
The energy of the recoil nucleus is negligible or we have to consider it for calculation?
yes sir.
very nicely explained.
sir how can we write momentum conservation equation for annihilation?
Check this if it is right...
initial momentum=final momentum
0 = hf/c+(-hf/c)
hf/c=hf/c.
@suman
its energy is negligible due to large mass.so that we don't need to consider it for calculations.
An electron-positron pair can't annihilate into a single photon, for precisely the same reason as a single photon in vacuum can't convert into an electron-positron pair. Such a process wouldn't satisfy the law of conservation of momentum.
Sir
If a no. B/w 0 and 1 is multiplied to any no. The result that comes is smaller than the original no.
Hence here when you multiply by v/c and cos⁰ you are using a no. Which is b/w 0 and 1 and as you are multiplying it with 2(gamma)m⁰c² then the result that we arrive is hv>2(gamma)m°c²
But you have written hv
What a clear explaination ! Hand moves ,eye contact , clear tone and accent everything is so perfect with this man ...can't help falling in love with the way he teaches .
Another great video, from a master teacher, please make more theoretical videos for example on Quantum field theory
Brilliant explanation. I've been a physics teacher for 12 years and this guy is great
WOW! your writing is so neat even on a green board with chalk,
I got this question in my last exam...i was lucky if i got this explanation before my exam..whatever i got the right explanation at last... Thanks sir
I think I've found THE physics channel in the Indian youtube space, and I have seen them all. Your presentation is very clean, your articulation very precise and these are the two things I found lacking in the others. Great lesson!
I remember when you had less than 2k subscribers . I believed in you. I'm really happy for what you achieved so far. Love from Morocco
Thank you :)
This video is one of the best demonstration of clarity of concepts....
Great penmanship.
Nice and humble person with so much ability
Beautiful description!
Hey sir!! I am going for interview fir TIFR this year that's why I am preparing... I had a lot of confusions related to pair production but now all has been cleared.... So thanks ❤❤❤🙏🙏🙏🙏
You are the best! No textbook nor website nor video explains this as well as you.
thank you very much, Sir...... God bless you....
Very fortunate to find this
Heartiest gratitudes
Amazing video! Very informative!
8:20 I would say the positron has momentum: p(+) = p . cos(- theta) = - p . cos(theta). So the momentum of the photon (p) should be equal to the difference: p(-) -/- p(+); with p(-) being the momentum of the electron. Then the min-sign vanishes and we get this 8:56. And here 11:04 we should have "a bigger than"-sign (>).
cos(-x)= cos(x)
the -ve doesn't come out
Very good lecture sir.. Thanks a lot
Thank you sir for explaining this topics elegantly.................. :)
1. Can a free electron absorb a photon?
ua-cam.com/video/QRCSlbOhMFU/v-deo.html
2. Can you Prove E=MC² ?
ua-cam.com/video/VZEhmWFlrnM/v-deo.html
3. What is a Black Hole? Understanding the first ever image of a Black Hole
ua-cam.com/video/WuYpI3EoCnM/v-deo.html
Truly appreciate ur knowledge
Very good explanation sir
I'm in love with this man
Thankyou for your detailed information.
Very very informative video.... Thank u very much sir
Way of explaining is extermely Aesthetic 👍👍
This is great explanation sir🙏🙏🙏🙏👍👍👍
To be honest, sometimes I could not bear with Indian teachers because their accents are too strong and it's hard for me to understand, but this teacher is absolutely amazing. He explained the whole process clearly with beautiful handwriting and intonation. Thank you
Great video sir.. it was very clear and easy to understand
Thank you so much sir
Really nice and easy to understand proof. Thanks!
you are boss of physics
Sir, please upload more videos of various topics.
an awesome explanation thanks
Sir your language is so impressive
Great explanation..
Excellent Explanation and Content
very well explanation
Good explanation.
perfect explaination sir
It's a very amazing video. Solved my problem! Thank you!
Good explanation
M watching ur nuclear vedios especially.... Great effort... ❤️From Pakistan...
You should have a look at EWT video about annihilation.
Very nice explaination
Sir when I saw your video then I thought that it's done
equation (ii) should be written as hf>2gamma m0c^2. Thanks
Seems that if pair creation only required energy of a certain level, it would occur in ALL conditions that involves high energy, which would include any such high energy photon travelling in vacuum. It simply cannot be a high energy photon on it's own. It MUST impact something. While it's far more likely for the photon to encounter a target in non vacuum environments, that does not logically translate to "cannot happen in vacuum" but rather it is UNLIKELY for a collision to happen in vacuum, but it CAN happen
I'm pretty sure it's clear that the question is about a pure vaccuum, not one where a collision with some particle is possible. And if there's a particle there, then the neighborhood containing that particle isn't a pure vacuum. What you want to say is that photons in space in this universe can impact particles because IRL space is full of particles, just very sparsely populated in some places at some times, therefore we should see particle creation at some rate in any appreciably-sized region of IRL space.
Great video, thank you very much!
Amazing video! Keep up the good work
wonderful video
My suggestion is that:
1. the singularity before the Big Bang was all photons, and
2. that the universe was made by pair conversion where photons make electron positron pairs.
Readers challenge me with, how can you prove that?
Most of it has already been proved!
These 3 things that we know are true, support many of my ideas on the importance of photons in physics
1. Photons are outside of time and distance.
2. Photons create an electron positron pair in pair conversion. ( During extreme conditions photons can create proton, anti proton pairs; and neutron, anti neutron pairs).
3. Should all the mass be converted to energy, we would have a universe of photons.
Awesome explanations ♥️
Great....thank you so much sir
Thank you so much sir..I have few confusion about how nucleus help to conserve energy and momentum. Now it's very clear . This question was asked me in PhD interview at IIT indore but I was unable to explain them clearly and got rejected. Thank you sir for clarity.
Please refer me that why we can't measure simultaneously position and momentum conceptually..
🙏🙏
How you will measure position?
You have to draw a position vector but measurement will take some time.and measured value will be different from actual value.larger the speed larger will be the error.hope it works.
Awesome video. 🌟
good work!
Great work
Masterpiece
Well, you didn't explain the momentum conservation for pair annihilation. I got stuck at that place, where I don't know how to prove simultaneous momentum and energy conservation for pair annihilation.
Great.sir I have a question. How matter and anti matter arose from energy after big bang then? Wasnt there vaccum and energy only?
Thank you sir..this video helped a lot
I have no words except wowwwww
Sir, it also proves that ..nothing is really needed for destruction of masses(pair annihilation).. but construction or creation(pair production) needs some material!!!..
Good effort
Fantastic lecture with lucid explanation. Keep it up Dibya.
Thanks a lot :)
Hey, sorry for resurrecting an old video. I have a questions though - if annihilation in vacuum is possible, but a pair creation isn't, doesnt this violate the time symmetry? Thanks.
Sir ur nuclear physics lec,s are best so please start also atomic and molecular physics if possible
Thanks
Thanks. But I dont know how to calculate : gamma mc square. What is the value of gammm in this equation?
Why it needs a medium? what specific interaction happens in pair production?
Suggestion: you should make videos on non-interial reference frames and about acceleration in special relativity.
Also about dirac's Unification of quantum mechanics with special relativity.
I will come to STR once I am done with nuclear..
Thank you..
What happens to the combined MASS of electron and positron pair when on annihilation they become gamma rays? So gamma ray photons must have mass?
Nice video.... Sir plez make videos for solving quantum numticals
Thank u sir...
Nice sir i follow your video
No sir, Thank you very much
I have a little question that during the pair-production, as the Positron is created from the hole in the negative energy state and also the electron goes to the positive energy state, it doesn't mean that every -ve energy state region can produce this electron-positron pair? I mean to say that from Dirac's theory, he considered vacuum as a sea of negative energy but as you showed pair production can't happen in vacuum, so that means there can be negative energy region but that doesn't mean that pair production can happen there?
very nice video sir....
Thanks sir best description.we say that proton is a stable particle but As the consequences of Grand unification theory it is an unstable particle so what is this?
Stable means it has a very large half life. It doesn't mean that it is a fundamental particle. Infact a proton is not fundamental. Still it is quite stable, and proton decay has not yet been experimentally observed.
Sir please make a video on Ghoshal experiment.
i got answer, awsome class . thank u sir
Awesome
great teacher ever but u speak very fast sir😊
I have a question in my mind if u can clear it sir?? If a photon of energy 1.02Mev creat an electron positron pair then the electron positron pair must be at rest because all of the energy of photon is converted to mass. Now if momentum of the photon is non zero and the momentum of the electron positron pair is zero which means momentum is not consereved. My question is that as all the mementum is used in recoiling of the nuclesus??
Contradiction same as for 1st case too....if we do conservation of momentam then also we got contradictive result..
Although mass energy equivalence of special relativity allows conversion of a photon to an electron-positron pair, such a process cannot occur in free space because
A mass is not conserved
B energy is not conserved
C momentum is not conserved
D charge is not conserved
Why
I've a question... that how nucleus carries away photons momentum for pair production to occur?
In electron positron annihilation negative and positive charge appearto split among emerging photons. If photon carries partial charge then in pair production how can it produce electron and positron each of which carry full charge.
Its really nice to watch your explanations, sir.. however, isnt it two oppositely directed annihilation photons of energy 511Kev.. (which is the priniple of detection of positrons in PET scan )?
Exactly, two photons 180 degrees apart.
great lecture but how did law of conservation of energy take place here it is against the law of conservation of energy
Thank you sir
Sir please make a video on Dirac hole theory
Will do soon..
What is the difference between a proton ,a positron and a photon?
A photon is an elementary particle, a quantum of light (or electromegnetic radiation). It has no electric charge or rest mass.
A positron is an elementary particle, an antiparticle of an electron. It has rest mass of about 0.5 MeV, and positive electric charge (same magnitude but opposite sign than an electron).
A proton is a composite particle (it consists of quarks). Protons and neutrons are together called nucleons, because they appear in an atomic nucleus. It has rest mass of about 938 MeV (about 1800 times the mass of an electron), and a positive charge of the same magnitude as an electron.
Nice
Why did you get c*c*(v/c) in the second equation after multiplying c*v by c? Shouldn't it just be c*c*v?
What if one may take two counter propagating photons for the pair production case in vacuum.
Thanks. But it looks like it is also impossible for the photon without splitting into two directions during annihilation. it will disobey the conservation of momentum as well.
photon do split but sir doesnt mention