Yep. My wife sees no reason why she shouldn't use the washing machine just because I am recording a video! In some videos you can probably hear the vacuum cleaner - not to mention a kitchen clocks that moos and a dog that barks. Oh the trials of being a physicist!
You go through this in such a linear, understandable manner. You have a gift for teaching, don't ever stop. Im writing a huge paper for my final, which counts 2x a normal final grade, and this video basically sums up all i need, and gives me a brilliant outline for the paper. Thank you so much.
This is INCREDIBLY FASCINATING!!! I'm only at GCSE and my school fails to be interesting, but I like physics and this was brilliant :) Thank you :)))))) My mind is blown and on the ceiling in pieces....Now I can't wait for a-level physics :)
I think it's at 5:52 where the φ sign mysteriously appears. You are, of course, quite right. Either that which is marked φ is actually φ/h (since if KE = 0 then hf = φ) or I should extend the y axis downwards and the point at which the line crosses the y axis would be KE = -φ (since f=0). I've added an annotation.
Yes it is. And I use that value later in the vldeo. It's just that the questions I was answering in the earlier part of the video assume the value of h calculated in the early question. I hope I added a comment to make clear the actual value of h.
Thanks. The full playlist of my A level physics revision videos is given in the description box above. I have attempted to cover all the material in the main A level physics courses but if there is a particular A level area you think I have missed let me know and I'll try to do a video on it.
Bless you Dr Physics - you enable me to help my 17 year old grandson with his physics revision - and get me interested too. Everything's explained so clearly and economically. What a generous gift your lessons are!
Not rude at all. Glad they are of help. Should be up sometime early next week. It will be basic addition, subtraction, dot product and cross product for vectors.
I am saying that the part of the x axis which is labelled φ should be φ/h. The reason is that Kinetic Energy of the emerging electron is the energy of the incident photon (hf) - the binding energy or work function (φ). So KE = hf - φ. On the x axis KE = 0. So hf=φ. So f=φ/h. The x axis is a measure of frequency and when the y axis (KE) = 0 then f = φ/h
HOLY CRAP! You, my friend are awesome! This is the first video of yours that I have watched, and it's like these were made just for me, because I'm good at catching on quickly to things, and I really like to see the formulas derived and the history behind it, just spectacular!
Good question. I think the real problem for us is that we operate in the real classical world rather than the world of quantum mechanics. We have adopted the idea that the electron is a particle and therefore it is very difficult to imagine how a single particle could behave like a wave passing through two slits. But quantum field theory suggests that actually everything is made of fields and particles are simply expectations of those fields.
great! i'm not studying physics but your videos show that understanding subjects through equations and math can be very simple.... actually, i find this more understandable than most of the "simple-approaching" videos from channels that are for some reason far more well known than yours..
The particle nature of light comes from the fact that it transfers energy in discrete, quantised packages rather than a continuum which you might expect of a wave.
An elastic collision means that KE is conserved. In an inelastic collision it is not. Total Energy is always conserved but in an inelastic collision some of that kinetic energy is converted to other forms of energy eg heat. Momentum is always conserved.
Its the consequence of quantum mechanics. Everything is both a particle and a wave. I suppose you would call it a Schrodinger Wave since it is his equation that the wave obeys. The problem is that for all bar atomic particles, the wavelength is so small that there is no way of measuring or detecting it.
Basically yes on all counts. Ionising radiation is radiation that carries enough energy to liberate an electron from an atom. Atomic vibration arises when an atom absorbs a quantum of energy (E = hν). But temperature can't really be applied to one atom. Temperature is a measure of the collective energy of all the atoms/molecules in the substance.
Good Old Al. Who else would understand the significance of the flat line from zero to phi as an indirect measure the "binding energy" within the atom itself that needs be overcome to account for the electron's ejection.
Funnily enough, these videos teach me better than My physics teachers, so erm, well done :D great videos, helping me with my A-Levels so much :D thanks
I've only watched this video and hit subscribe. I love your coverage of wave particle duality over all others I have seen. I would only nitpick that you phi looks like an empty set symbol. I don't think that it would be confusing to most people since you state the name several times, and anyone already familiar will know which slashed cycloid they're meant to interpret from the math in which it appears.
And, if this is the case, I'm assuming that this jumping up causes an increase in the intensity of atomic vibration, being perceived as an increase in temperature. Is that correct? And, if this is the case, then radiational cooling happens when the electron jumps back down, releasing a photon with a frequency in the infrared range and slowing the vibration of the atom. Is that correct? Any feedback would be greatly appreciated. Thanks!
Could the wave particle duality of light be acting like the bits or zeros and ones of a computer? In this theory the physics of quantum mechanics represents the physics of ‘time’ as a physical process. The spontaneous absorption and emission of light is forming a blank canvas that we can interact with turning the possible into the actual within our own ref-frame! Time is an emergent property with the future coming into existence photon by photon relative to the actions of the atoms.
Thank you! Although I'm a bit confused with the work function- why is it the x-axis intercept and not the y-axis intercept? if y=mx+c -> Ke=hf - φ surely work function is c (y-axis intercept)? Thanks!
Animation I don't think I said that photons had mass. On the contrary I was making the point that since they are massless its not obvious how they can have momentum = mv
One postulates if there would be a mass so great as to produce a wave smaller than the Plank length? Would it be possible, one assumes not and the point of nearing it would be when the resultant gravitational waves would become energetically powerful enough to crush it out of existence in the forming / form of a black hole??
Hi, Excellent video! I'm trying to understand radiant heat transfer. If I understand correctly, electromagnetic radiation that happens at frequencies greater than the threshold frequency is what we'd refer to as ionizing radiation. Is that correct? And, if that's the case, infrared heat transfer is non-ionizing and as such does not strip electrons from the atom, but rather causes them to "jump up one orbit". Is that correct? (continued in the next post)
What a beautiful colorfullness photons, Saleh Theory, for the first time, explain the relationship between different colors and different Gyroradius Helical motion of photon. see new difinition of colorfulness of photon video on saleh theory-com chanel.
why can electrons (or any particle) behave as waves? i understand the mathematical formulae governing this principle, but what physical properties does electrons have on an atomic scale that permits it to pass through two slits at the same time? and what is its waveform? (i suppose there aren't oscillation of particles, so how does the wave of an electron look like? how can its wavelength be observed from its wave profile?)
I'm choosing my a level options and I was wandering whether physics was too hard to get an a/a* in. I'm really interested in physics but from what i've heard, it's like the hardest a level you can take. What do you guys taking it think?
Hello...First of all thank you very much for these lessons...I want to ask a question...What is the atomic scale explanation of electromagnetic radiation sometimes behave as wave sometimes behave like a photon? Is the reason of this phenomenon coming from the fact, the moving charged particles (so the sources of electromagnetic fields) sometimes behave like waves and sometimes behave like particles?
Sir,your videos are so so helpful for my revision in Physics...and sir,is that the collision between a Photon and the electron is elastic is the kinetic energy conserved....
If the electron is a wave, what happen when the electron does not travel? I meant from the equation that you had proven on 12:35..if the electron doesn't travel, velocity equal zero...then we will get infinite wave length?
So does a single photon take the form of a Gaussian wave packet? I've read classical E&M and then QM. I know planar waves are an approximation of light in general, but what is a single photon, and what is a modern model with quantization included. Thanks.
at 16:30 you substituted "v" as root "m/2ev" when "v" = root "2ev/m". That is something that confused me. But then we substitute correctly and put m inside the root as m^2 on the third step and everything makes sense. Could you please put annotation on the video at 16:30 for people watching in the future. Great videos, many thanks :)
@DrPhysicsA if light is wave: why do we need the double slit? why can't we use two sources of light and shine them together in a way they interfere? ( consider the 2 hols in the double slit as source of light so why cannot we do it directly from 2 source of light whithout the double slit? ) and another question when the light hit the screen as interference pattern they are also bouncing back to our eyes so we can see them, why they dont interfer as well before coming to our eyes.. ? would you answer me back?
we use a double slit to keep the waves coherent, this means they have a constant phase difference and so they can demonstrate constructive/destructive interference. if we use two sources of light and shine them together they wont interfere because the waves are not monochromatic and they are not coherent. someone please correct me if im mistaken. also for your second question i think it is because the pattern is projected on a screen and it not shone right back
you could measure the wavelengths if you had enough humans together unite for a singularity time or times in which every person sent a text to a person on their top five on their cell or chimed a sound or shut off and turned back on their houselights, without blowing up everything so planning the logistics around it... I'm trying to gather a force like that, if you know any scientists into trying to measure that let me know... give gravitational force to people trying to clean up power currently
Yea, but u're missing the important points in the video, like the intensity of the light in the photoelectric experiment and things that explains it cant be described as wave. U went directly to the conslusion that it's particles becuase it can transfer energy to the electron.
In the video you kept saying the photons give the electron enough energy to come out of the atom. But aren't the electrons already delocalised within the metal and we're never actually in the atoms of the metal? They just leave the surface of the metal from amongst the atoms not in the atoms
Piers Reynaud No. Otherwise you could get the photoelectric effect with visible light since there would be virtually no minimum energy threshold required.
At time 5.50 you have labelled phi on the horizontal axis by error, because it should be on the negative part of the vertical axis. Clearly phi must have units of energy!
I've watched videos like this so many times and I still don't get it. I've got to the point I can't even look at videos that say light's wave - particle duality is wrong and know enough to find fault in their arguments. The consensus seems to be that light has this wave particle duality and therefore anyone saying it does not have this duality must be some nut. Am I wrong?
U say light is particles because it can transfer energy to the electron but u dont explain why. Its the same as saying light is a wave because it can transfer energy to the electron?
would say Jim is a man of humility. He won't mind. But thank you so much for providing these beautiful explanations. I was reading Susskind's book "Quantum Mechanics: The Theoritical Minimum". Halted after 39th page. Got to your video on Dirac Notation. Now I am on a rampage on the aforementioned book. Many thanks.
![Felix "Unfair" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/Oswujxm2Ag0/mqdefault.jpg)
Yep. My wife sees no reason why she shouldn't use the washing machine just because I am recording a video! In some videos you can probably hear the vacuum cleaner - not to mention a kitchen clocks that moos and a dog that barks. Oh the trials of being a physicist!
Studying through videos is much more fun than the book! Thanks a lot for uploading these, very very helpful man I appreciate it
You go through this in such a linear, understandable manner. You have a gift for teaching, don't ever stop. Im writing a huge paper for my final, which counts 2x a normal final grade, and this video basically sums up all i need, and gives me a brilliant outline for the paper. Thank you so much.
This is INCREDIBLY FASCINATING!!! I'm only at GCSE and my school fails to be interesting, but I like physics and this was brilliant :) Thank you :)))))) My mind is blown and on the ceiling in pieces....Now I can't wait for a-level physics :)
Thanks. I'm thinking of doing a short video on vector addition, subtraction, and multiplication (dot and cross product). It's in the queue.
I think it's at 5:52 where the φ sign mysteriously appears. You are, of course, quite right. Either that which is marked φ is actually φ/h (since if KE = 0 then hf = φ) or I should extend the y axis downwards and the point at which the line crosses the y axis would be KE = -φ (since f=0). I've added an annotation.
Yes it is. And I use that value later in the vldeo. It's just that the questions I was answering in the earlier part of the video assume the value of h calculated in the early question. I hope I added a comment to make clear the actual value of h.
Thanks. The full playlist of my A level physics revision videos is given in the description box above. I have attempted to cover all the material in the main A level physics courses but if there is a particular A level area you think I have missed let me know and I'll try to do a video on it.
Yes. And that is another way of expressing the uncertainty principle. If v=0 then p=0 (known for certain). Thus position is totally unknown.
Bless you Dr Physics - you enable me to help my 17 year old grandson with his physics revision - and get me interested too. Everything's explained so clearly and economically. What a generous gift your lessons are!
That is very kind of you to say so. All good wishes to your grandson for his exams.
---- PAY ATTENTION TO THE VIDEO----
ty, needed this
Lenses etc are covered in Geometric Optics - A Level Physics in the A Level Revision playlist. I shall be uploading a vid on sampling next week.
Not rude at all. Glad they are of help. Should be up sometime early next week. It will be basic addition, subtraction, dot product and cross product for vectors.
I am saying that the part of the x axis which is labelled φ should be φ/h. The reason is that Kinetic Energy of the emerging electron is the energy of the incident photon (hf) - the binding energy or work function (φ). So KE = hf - φ. On the x axis KE = 0. So hf=φ. So f=φ/h. The x axis is a measure of frequency and when the y axis (KE) = 0 then f = φ/h
HOLY CRAP! You, my friend are awesome! This is the first video of yours that I have watched, and it's like these were made just for me, because I'm good at catching on quickly to things, and I really like to see the formulas derived and the history behind it, just spectacular!
I've just done a video on single and double slit experiments and diffraction gratings.
Yes provided the energy in the photons (E=hf) is greater than the work function (binding energy) of the electron to be liberated.
I literally cannot thank you enough, these videos are so good, i wouldn't understand a thing if it weren't for watching these
Good question. I think the real problem for us is that we operate in the real classical world rather than the world of quantum mechanics. We have adopted the idea that the electron is a particle and therefore it is very difficult to imagine how a single particle could behave like a wave passing through two slits. But quantum field theory suggests that actually everything is made of fields and particles are simply expectations of those fields.
great! i'm not studying physics but your videos show that understanding subjects through equations and math can be very simple.... actually, i find this more understandable than most of the "simple-approaching" videos from channels that are for some reason far more well known than yours..
Many thanks for your kind words. Hope all goes well in the final paper.
These videos are unreal, Kinna simplifies it from the books.. Well, as simple as its gonna get
Try "Geometric Optics - A Level Physics" for lenses. I haven't done anything on sampling.
Thank you very very very much for your excellent classes. You are a *far better* teacher than the competition I have tried.
Hi Dr Physics A, thank you for all these videos you've uploaded on youtube! You've helped me so much that I have no idea how I can repay you!
What a detail teaching, most lectures would just skip how de Broglie arrived at p=h/lamda by starting with E=mc^2 @10:15
this video connects as and a2 parts of wave particle duality.very very help ful
You're videos are so helpful thank you so much for making some of these complicated theories much easier to understand.
The particle nature of light comes from the fact that it transfers energy in discrete, quantised packages rather than a continuum which you might expect of a wave.
Great as always
An elastic collision means that KE is conserved. In an inelastic collision it is not. Total Energy is always conserved but in an inelastic collision some of that kinetic energy is converted to other forms of energy eg heat. Momentum is always conserved.
Thank you! The books we use explain things in such a poor way, sometimes it's so much better to just draw it all out and explain things simply!
Its the consequence of quantum mechanics. Everything is both a particle and a wave. I suppose you would call it a Schrodinger Wave since it is his equation that the wave obeys. The problem is that for all bar atomic particles, the wavelength is so small that there is no way of measuring or detecting it.
You are simply amazing at explaining this, I really can't thank you enough for this explanation.
Chiarissimo, come sempre. Clear, as always.
Basically yes on all counts. Ionising radiation is radiation that carries enough energy to liberate an electron from an atom. Atomic vibration arises when an atom absorbs a quantum of energy (E = hν). But temperature can't really be applied to one atom. Temperature is a measure of the collective energy of all the atoms/molecules in the substance.
❤❤ Physics Equation plus Drphysics Perfect Combination for Understanding.
Thank you so much! I was having trouble with this in my chemistry class and this has cleared much of the confusion.
Good Old Al. Who else would understand the significance of the flat line from zero to phi as an indirect measure the "binding energy" within the atom itself that needs be overcome to account for the electron's ejection.
Funnily enough, these videos teach me better than My physics teachers, so erm, well done :D great videos, helping me with my A-Levels so much :D thanks
I've only watched this video and hit subscribe. I love your coverage of wave particle duality over all others I have seen. I would only nitpick that you phi looks like an empty set symbol. I don't think that it would be confusing to most people since you state the name several times, and anyone already familiar will know which slashed cycloid they're meant to interpret from the math in which it appears.
And, if this is the case, I'm assuming that this jumping up causes an increase in the intensity of atomic vibration, being perceived as an increase in temperature. Is that correct?
And, if this is the case, then radiational cooling happens when the electron jumps back down, releasing a photon with a frequency in the infrared range and slowing the vibration of the atom. Is that correct?
Any feedback would be greatly appreciated. Thanks!
This is a fantastic channel :)
Could the wave particle duality of light be acting like the bits or zeros and ones of a computer? In this theory the physics of quantum mechanics represents the physics of ‘time’ as a physical process. The spontaneous absorption and emission of light is forming a blank canvas that we can interact with turning the possible into the actual within our own ref-frame! Time is an emergent property with the future coming into existence photon by photon relative to the actions of the atoms.
Thank you! Although I'm a bit confused with the work function- why is it the x-axis intercept and not the y-axis intercept? if y=mx+c -> Ke=hf - φ surely work function is c (y-axis intercept)? Thanks!
At 10:40 ,you said that photon could be either mass or energy ?
How it could be mass?
Animation E=mc^2
Animation I don't think I said that photons had mass. On the contrary I was making the point that since they are massless its not obvious how they can have momentum = mv
Animation Photons have momentum though
Thank you so incredibly much for your wonderfully clear videos DrPhysicsA :)
One postulates if there would be a mass so great as to produce a wave smaller than the Plank length? Would it be possible, one assumes not and the point of nearing it would be when the resultant gravitational waves would become energetically powerful enough to crush it out of existence in the forming / form of a black hole??
Hi,
Excellent video! I'm trying to understand radiant heat transfer. If I understand correctly, electromagnetic radiation that happens at frequencies greater than the threshold frequency is what we'd refer to as ionizing radiation. Is that correct?
And, if that's the case, infrared heat transfer is non-ionizing and as such does not strip electrons from the atom, but rather causes them to "jump up one orbit". Is that correct?
(continued in the next post)
What a beautiful colorfullness photons, Saleh Theory, for the first time, explain the
relationship between different colors and different Gyroradius Helical motion
of photon. see new difinition of colorfulness of photon video on saleh
theory-com chanel.
Sorry, but i'm not quite sure how you got m into the square root to get h/root2meV. at 16:18 thank you.
I took the m outside the square root and made it m^2 inside the square root.
You teach this really well, thank you!!
why can electrons (or any particle) behave as waves? i understand the mathematical formulae governing this principle, but what physical properties does electrons have on an atomic scale that permits it to pass through two slits at the same time? and what is its waveform? (i suppose there aren't oscillation of particles, so how does the wave of an electron look like? how can its wavelength be observed from its wave profile?)
I'm choosing my a level options and I was wandering whether physics was too hard to get an a/a* in. I'm really interested in physics but from what i've heard, it's like the hardest a level you can take. What do you guys taking it think?
Hello...First of all thank you very much for these lessons...I want to ask a question...What is the atomic scale explanation of electromagnetic radiation sometimes behave as wave sometimes behave like a photon? Is the reason of this phenomenon coming from the fact, the moving charged particles (so the sources of electromagnetic fields) sometimes behave like waves and sometimes behave like particles?
Sir,your videos are so so helpful for my revision in Physics...and sir,is that the collision between a Photon and the electron is elastic is the kinetic energy conserved....
appreciate ur quick respone ill let u know if u missed any topic.edexcel only
If the electron is a wave, what happen when the electron does not travel? I meant from the equation that you had proven on 12:35..if the electron doesn't travel, velocity equal zero...then we will get infinite wave length?
Dear Sir, do you have any videos on atomic spectra?
So does a single photon take the form of a Gaussian wave packet? I've read classical E&M and then QM. I know planar waves are an approximation of light in general, but what is a single photon, and what is a modern model with quantization included. Thanks.
Excuse me. Is it possible to have photoelectric effect when electrons strike semi-metal like graphite?
at 16:30 you substituted "v" as root "m/2ev" when "v" = root "2ev/m". That is something that confused me. But then we substitute correctly and put m inside the root as m^2 on the third step and everything makes sense. Could you please put annotation on the video at 16:30 for people watching in the future. Great videos, many thanks :)
Well actually I substituted for 1/v which is why I inverted the term for v.
I'm not quite sure what your annotation meant at 05:52
ur videos are really helping lot of edexcel student.can u make videos on edexcel alevels physics
@DrPhysicsA if light is wave: why do we need the double slit? why can't we use two sources of light and shine them together in a way they interfere? ( consider the 2 hols in the double slit as source of light so why cannot we do it directly from 2 source of light whithout the double slit? ) and another question when the light hit the screen as interference pattern they are also bouncing back to our eyes so we can see them, why they dont interfer as well before coming to our eyes.. ?
would you answer me back?
we use a double slit to keep the waves coherent, this means they have a constant phase difference and so they can demonstrate constructive/destructive interference. if we use two sources of light and shine them together they wont interfere because the waves are not monochromatic and they are not coherent.
someone please correct me if im mistaken.
also for your second question i think it is because the pattern is projected on a screen and it not shone right back
Thank you so much Dr.
If waves pass through a medium, what would the medium be for a macroscopic object behaving as a wave?
awsome explanation really helpful for my physics class
Thank youuuu for this video.
Wow , loved it , very clear
Fantastically explained :)
Thank you very much 👍🏻👍🏻👍🏻
very helpful, A big thank you
8:00
you could measure the wavelengths if you had enough humans together unite for a singularity time or times in which every person sent a text to a person on their top five on their cell or chimed a sound or shut off and turned back on their houselights, without blowing up everything so planning the logistics around it... I'm trying to gather a force like that, if you know any scientists into trying to measure that let me know... give gravitational force to people trying to clean up power currently
Does anyone know a tutor similar to drphysics but in an another AL?
See reply below to madtigger24
So to work out the wavelength of the Earth.
H = 6.64E-34
M = 5.972E24
V = 30,000 m/s (orbit around the sun)
Does this mean the Wavelength is 3.7E-63m?
James Seymour Probably. I haven't checked the maths, but as you have demonstrated the wavelength of the earth is immeasurably small.
It is relative..
These are great Thank you so much
What is threshold energy?
Rakesh Prasad It usually means the minimum energy needed to get something to happen.
+DrPhysicsA Is this the same as threshold frequency?
Thank you sir. what is your name?
What is secondary wave?
Animation If you mean as in earthquakes you can look up S wave in wikipedia or see my video on seismic waves ruclips.net/video/K7SEQ3qlW7g/видео.html
Waves don't necessarily pass through a medium. Electromagnetic radiation can pass through a vacuum.
Yea, but u're missing the important points in the video, like the intensity of the light in the photoelectric experiment and things that explains it cant be described as wave. U went directly to the conslusion that it's particles becuase it can transfer energy to the electron.
Oh okay, that's great. Have my exam on Monday so got a little worried for a second!
In the video you kept saying the photons give the electron enough energy to come out of the atom. But aren't the electrons already delocalised within the metal and we're never actually in the atoms of the metal? They just leave the surface of the metal from amongst the atoms not in the atoms
Piers Reynaud No. Otherwise you could get the photoelectric effect with visible light since there would be virtually no minimum energy threshold required.
DrPhysicsA in which case my physics teacher is wrong
Piers Reynaud You might want to google "Photoelectric effect and Compton effect"
DrPhysicsA yeah I know about those
At time 5.50 you have labelled phi on the horizontal axis by error, because it should be on the negative part of the vertical axis. Clearly phi must have units of energy!
Your presentations are still wonderful though!
great videos!
Thank you proffesor
You are a good man.
Is h not 6.63*10^-34?
I've watched videos like this so many times and I still don't get it. I've got to the point I can't even look at videos that say light's wave - particle duality is wrong and know enough to find fault in their arguments. The consensus seems to be that light has this wave particle duality and therefore anyone saying it does not have this duality must be some nut. Am I wrong?
really helpful
U say light is particles because it can transfer energy to the electron but u dont explain why. Its the same as saying light is a wave because it can transfer energy to the electron?
thankyou
Does this means every particle has a wavelength?
+Daniel Skiba
Yes
Is this Jim Al Khalili? I am not 100% sure but the voice sounds like Jim Al Khalili.
I'm flattered tho I doubt that Jim would be.
would say Jim is a man of humility. He won't mind. But thank you so much for providing these beautiful explanations. I was reading Susskind's book "Quantum Mechanics: The Theoritical Minimum". Halted after 39th page. Got to your video on Dirac Notation. Now I am on a rampage on the aforementioned book. Many thanks.
wtf, a ball has a wavelength? if it could be measured what kind of wave that would be?
I said joules per second and he replied, "not joules per second but joules second".
No physicist to day is
Better than you
Studying in 2019
2020