I can't believe nobody's commented on how awesome his accent is yet.
@robertfinkle9020
8 жыл бұрын
+candleinthewind "something to add about the CURRENT!"
@cowardlyheroine
8 жыл бұрын
+candleinthewind He sounds a bit like Baymax? I'm only saying this because I watched Big Hero 6 recently :)
@yesiamadorito
7 жыл бұрын
OMFG IT WASN'T JUST ME
@ToDie4r
7 жыл бұрын
true, it plays big role in making us understand better
@parksliderbarricade4324
7 жыл бұрын
He reminds me of my Further Maths teacher. He's so enthusiastic and it's beautiful.
@johnmontgomery560
9 жыл бұрын
I love your lectures. When I retired I was considering going back to university to study physics. Now I can do it at home with a superb lecturer John
@missabcgirl123
10 жыл бұрын
learnt more in 36 minutes then i have in the entire year
@Benjones96
10 жыл бұрын
Glad im not the only one xD
@DrPhysicsA
10 жыл бұрын
I hope it has proved helpful in any exams you may have been taking.
@krcd-eb6kb
7 жыл бұрын
Beth Jackson agreed
@ToDie4r
7 жыл бұрын
exactly :)
@nataliaperez9372
5 жыл бұрын
me right now
@sandorclegane2485
9 жыл бұрын
I've never heard a clock that goes "mooo". Fascinating.
@yaseenahammed6352
9 жыл бұрын
Sandor Clegane I will eat every chicken in this room.
@finlaykingdon2063
3 жыл бұрын
hes British dont be racist
@DrPhysicsA
11 жыл бұрын
It covers material in the AQA, OCR and Edexcel syllabus and I have also added some material from the CIE syllabus. I cant guarantee that it covers everything. If anyone spots gaps, let me know and I'll try to add more videos to cover them.
@annepioquinto4784
8 жыл бұрын
Exam is tomorrow and I'm ready to go! Thank you immensely for making such digestible videos!
@DrPhysicsA
8 жыл бұрын
Thanks. Hope the exam went well.
@TheRealWorld-TateSpeach
6 жыл бұрын
What did you get?
@johnpaul4301
5 жыл бұрын
@@TheRealWorld-TateSpeach he failed with flying colors
@hadeedahmad9465
5 жыл бұрын
@@DrPhysicsA can you tell me how much this video covers the cie alevel waves topic? Does this leave anything out that is in the cie syllabus?
@snhtsljedc9803
4 жыл бұрын
Hadeed Ahmad do u still need an answer?
@ARaven5
10 жыл бұрын
woah, my physics exam is next week and this has helped me a bunch! amazing video, thank you!! (much better than my teachers:P)
@DrPhysicsA
10 жыл бұрын
Thanks. And all good wishes for the exam.
@DrPhysicsA
11 жыл бұрын
Thanks for your kind words. Glad they have been on some help.
@walshamite
11 жыл бұрын
This series is GREAT. At school (1960s), did General Science, ), not enough physics there. Following hobby of astronomy-cosmology, I've been aware of gaps needing knowledge. Using YT physics clips to fill my gaps. Kinda knew some of it, but back to basics makes me see relationships as never before. I can follow the math. In my 60s now, still love steep learning curves. I learn better these days, no exams, just the joy of knowing. Thanks a 10 to the minus 6. It's a joy. UR never 2 old 2 learn!
@MathPhysicsFunwithGus
4 жыл бұрын
Your videos are amazing! I am first year undergraduate physics major and I proved that e&m waves travel at c after watching your videos and I understand the whole derivation and proof and can do it on my own no problem! Thank you!
@deebarfield2633
11 жыл бұрын
Loving the fact there's so many people watching these videos as last minute revision! They're so informative and everything is explained really well! Thank you :-)
@pico5746
8 жыл бұрын
I've just started A-levels but I need to do really well so watching these early on should help with revision later on as i'll just need to recap
@DrPhysicsA
8 жыл бұрын
All good wishes with your studies.
@DrPhysicsA
12 жыл бұрын
Thanks for comment. I'm not really sure what the benefits of polarisation might be. Google suggests some. But polarised glasses will reduce the amount of light entering the eye and can also reduce reflected sunlight (glare) which is itself polarised.
@alext9067
7 жыл бұрын
I like the clock mooing. I will also add that these videos are of tremendous interest to me and that I appreciate your effort and your candidness in presenting them.
@DrPhysicsA
7 жыл бұрын
Well spotted. Its a cuckoo clock with a cow instead of a cuckoo!
@Jood9090
6 жыл бұрын
I like the way he explained!! I need this man guys!!!! he's explaining better than mt teacher, I feel that he's is understanding what he's saying not like the other only say what they know and he also explain slower. really I like this man!! and I need him also!
@fatimaposwal7894
9 жыл бұрын
Thank very much Sir! I respect teachers because they teach you what they love teaching and only those who have a passion to teach others teach to a good standard. May God guide you and be with you. Best wishes, physics student
@els257
11 жыл бұрын
Thank you, I am an A* Student and I have been struggling a lot with this unit and this has really cleared a lot of things up for me. Thank you so much for your help!
@heidigarbett97
10 жыл бұрын
youve genuinely made everything ive been taught in class become clear to me now
@NTye
11 жыл бұрын
This was brilliant, like having a revision lesson without being at school! But a lesson I can pause, rewind etc as often as I need to. I was really struggling with standing waves, but you've helped me, thanks a lot!
@DrPhysicsA
11 жыл бұрын
You are quite right. Its a moot point whether that counts as internal reflection. But as you say, beyond the critical angle it certainly is internally reflected.
@DrPhysicsA
11 жыл бұрын
I am magnifying the whole slit so it is of length d. The argument is that in the circumstances I describe, you can think of the slit as being of two halves (each of d/2). Light from any point in the top half will be exactly out of phase (ie will cancel out) light from the corresponding point in the lower half. So all the light from the top half cancels the light from the bottom half (at the angle theta).
@DrPhysicsA
11 жыл бұрын
Lamda is defined as the wavelength - ie the distance between consecutive peaks in the wave. Frequency is defined by the number of wave peaks passing a point per second. The speed of the wave is the product of the two.
@bryonycoombs1018
10 жыл бұрын
BLESS YOU SIR I UNDERSTAND AND 2 DAYS BEFORE MY EXAM
@DrPhysicsA
10 жыл бұрын
Thanks. Hope the exam goes really well.
@MrKraftyy
10 жыл бұрын
OCR Electrons waves and photons? lol
@longdragon3
10 жыл бұрын
MrKraftyy can't wait for it. lol
@MrKraftyy
10 жыл бұрын
karan Naga lol i can wait, done it last yr and got a C. Ive been focusing on a2 so just started recaping yday lol
@parksliderbarricade4324
7 жыл бұрын
Just found this channel recently and this is perfect for getting a good grasp on Physics. Luckily, Physics is Linear so given I get a pass, I can use these videos to boost my grade greatly.
@mdk124
10 жыл бұрын
Really appreciate your effort going through all this! Not sure if i could have talked about physics for 30 over minutes!
@DrPhysicsA
11 жыл бұрын
Sorry about that. What we are saying is that as light passes through a double slit it will form a pattern on the screen which is a series of alternating light and dark patches (a series of black and white stripes if you like). These are called fringes. We usually call each light stripe the fringe and the distance between any two fringes is the distance from the peak whiteness of one to the peak whiteness of the next.
@DrPhysicsA
12 жыл бұрын
Much depends on where you draw the x axis. A trough isn't usually defined in that way. A trough is the point at which the wave reaches its lowest point on the y axis, just as a crest it where the wave reaches its highest point on the y axis. Eg y = sin x
@AmitMusicProductions
10 жыл бұрын
Sounds like the exam solutions guy..
@jorgegonzalez-ec5fl
7 жыл бұрын
This guy really knows what he's talking about. I'm glad we still have real teachers out there.
@Benjones96
10 жыл бұрын
you have saved my life.. and for that i am eternally grateful... exam tomorrow and found these vids which have cleared up so much! thank you! :D
@DrPhysicsA
10 жыл бұрын
Hope the exam goes really well.
@DrPhysicsA
11 жыл бұрын
sin r = 1 at the critical angle. This is the angle at which the angle of refraction is 90 degrees (ie along the surface of the water/glass). sin 90 =1. Beyond the critical angle, all the light is totally internally reflected.
@DrPhysicsA
12 жыл бұрын
This can get very philosophical. The speed changes and there is a compensating change in wavelength such that c=λf, but f itself does not change. The energy of the photons do not change (since E=hf). But the key point is that in order for you to see the colour the light has to leave the medium (glass, water etc) to travel thro your eye to your retina. So the only real sense of colour is that which is determined by the wavelength and frequency of light in your eye as it hits the retina.
@phynos8936
10 жыл бұрын
Wonderful video. Thank you.
@DrPhysicsA
11 жыл бұрын
They are permittivity of free space and permeability of free space respectively. I haven't done separate videos on them. For A Level it isn't necessary to know the detail of these constants.
@donaldcambridge1040
10 жыл бұрын
life saver. awesome video man
@dalemcmahon123
12 жыл бұрын
Thanks again. It makes sense now!!! The photon has to pass through the eyeball to reach the retina. The eyeball is gelatinous and will further slow down the light and change the wavelength depending on the refractive index of the eye material so it doesn't matter on what type of medium that the photon has to travel through before it reached the eye. Thanks a lot for replying!...........I have got it ! eureka !!
@DrPhysicsA
11 жыл бұрын
Path difference is just a measure of how much out of phase one wave is with respect to another. It can be measured in terms of wavelengths. But the key point is the fraction of a wavelength by which one wave is out of sync. This can be expressed either in terms of wavelengths of radians (2 pi rads = 1 wavelength). Frequency doesn't really afffect path length. No matter what the frequency two waves can be out of phase.
@DrPhysicsA
11 жыл бұрын
I don't have access to it. Is it on the web somewhere? Is there a link?
@DrPhysicsA
11 жыл бұрын
Thanks for kind comments. Quantum Mechanics is bizarre. We don't mean that particles travel as waves we mean that particles are waves. My advice for what it is worth, is that the best way of understanding quantum mechanics is not to try to equate it with anything in the classical world. Analogies can be helpful but are often misleading. Just accept that the quantum mechanics world is weird and counter-intuitive when compared with the classical world we inhabit.
@DrPhysicsA
11 жыл бұрын
At 21:00 I am showing a particular light wave which is at angle ϴ (ie the angle which will produce a dark patch on the screen). This means that at that angle, the light waves reaching that point on the screen are canceling each other out. Geometry relates ϴ, d and λ. So we show what the condition is for light waves to cancel out.
@pufalupagus
11 жыл бұрын
Great job i'm 16 yrs old and i understand this perfectly. Watching your lectures is a great pass time of mine
@DrPhysicsA
11 жыл бұрын
A good way to understand phase difference is to consider two waves with the same frequency, wavelength and amplitude which start out at different points. How far is the second wave behind the first one? You could give the answer in terms of distance - but that wouldn't tell us very much. We could give the answer in terms of wavelength. So if the second wave was half a wavelength behind then the two waves would be completely out of phase. Or you could regard each wavelength as 1 cycle = 2 pi rads
@ucingtigatiga
12 жыл бұрын
i agree,DrPhysicsA have great method explaining physics,to the point theoretically yet still engage intuitively.please expand your teaching by give problems to solve mr DrPhysicsA !
@jessicawhitney2074
6 жыл бұрын
I'm woefully unprepared for my resit tomorrow, this series of videos has helped a lot :) thank you for making these
@DrPhysicsA
6 жыл бұрын
Jessica Whitney all good wishes for the exam
@akshaypetta
11 жыл бұрын
This is probably the best thing to happen to KZitem. Thank You.
@asthav3000
8 жыл бұрын
Thank you soo much for these videos!! I really appreciate it, you've helped me a lot!
@DrPhysicsA
12 жыл бұрын
There are various ways photons interact with matter, but the key one for the issue you raise is that some photons give up all their energy as opposed to a partial loss of energy by all photons. For example a photon might transfer its energy (E-hf) to an electron and liberate the electron from the atom with an excess of Kinetic Energy that is eventually converted to heat energy. The photon beam would then be less intense but photons which had not interacted would retain their original energy.
@artemisangelique
9 жыл бұрын
is it too much to ask to make a diff playlist for As and A2? :c
@davidpenn4024
9 жыл бұрын
Yes.
@tanharahman9737
4 жыл бұрын
Artemis Angelique you might have already finished your A levels XD
@DrPhysicsA
11 жыл бұрын
Yes you rightly make the point that photons travel at c only in vacuum (and more or less in air). But slower in denser media.
@sandlertossone1813
4 жыл бұрын
Would love to hear a lecture on transmission line theory. Most video's online are not very helpful. I have watched almost all your videos and can say learned something new in each one. You have a special gift of taking complicated theory and relaying it simply to the everyday person.
@DrPhysicsA
12 жыл бұрын
It's already there. See my video on "Geometric Optics - A Level Physics". Go to my KZitem home page and select the A Level Physics playlist (on right hand side). you'll find it half way down.
@DrPhysicsA
11 жыл бұрын
Because for a small angle the hypotenuse and the adjacent are almost equal. So for small angles sin theta is the same as tan theta in terms of significant figures.
@HasanZobaer
7 жыл бұрын
Sir, you deserve more subs than pewdiepie !
@seanki98
7 жыл бұрын
Hasan Zobaer Amen
@alwwqe
6 жыл бұрын
lmao
@lightseeker2349
6 жыл бұрын
Every intellectual's utopian fantasy
@DrPhysicsA
11 жыл бұрын
Well frequency is one divided by the Period (T). T is measured in seconds. Frequency is measured in cycles per second. So frequency tells you how many cycles or wavelengths pass a particular point per second. T tells you how long it takes one wave to pass the given point.
@DrPhysicsA
12 жыл бұрын
@SailaMaham Yes that is exactly what happens. On a screen placed a few metres from the slit you will see an intense blob of light in the centre fading to a dark fringe then it become light again, then dark, although the flight areas become significantly less intense after that.
@quantum3280
4 жыл бұрын
Love watching these in 2020 quarantine
@shaahashareef8868
9 жыл бұрын
You are much better than any teacher in school. Thank you so much sir. You are awesome! 😊😄
@DrPhysicsA
11 жыл бұрын
I see some have responded already on this. As they say, EM waves all travel at the speed of light. The difference is their wavelength and frequency. But the produce of the two is always c. The more general answer is that EM radiation consists of massless photons whose energy is E=hf. All massless particles must travel at c. They cannot go slower, or faster.
@DrPhysicsA
12 жыл бұрын
The idea is that every point along the slit is a source of light so every point generates a light ray (the Huygens principle). I drew in the ones at the top and bottom of the slit and one in the middle. Then I show that every light ray in the top half exactly cancels the corresponding ray in the lower half.
@DrPhysicsA
11 жыл бұрын
If 2 waves are not in sync, then ask yourself by how much of a wavelength (or cycle) one lags behind the other. So suppose it is a quarter of a wavelength. Then you know that 1 wavelength = 1 cycle = 360 degrees = 2 pi radians. So now you can express the phase diff in degrees or radians or wavelengths. Where do I say n=1/2lamda?
@rachelbarn6011
8 жыл бұрын
You are God sent sir! Thank you so much for these videos
@laantful
11 жыл бұрын
Sir im an international student doing a levels in UK. i find it hard to learn in class bcs of the fast phase the teacher is teaching and its hard for me to understand his strong accent. but your video have helped me a lot through physics. Thank you so much. God bless.
@cadkls
10 жыл бұрын
You draw such beautiful waves.
@sekhar018
4 жыл бұрын
Most underrated channel with the best content..😑
@aki957
9 жыл бұрын
Thank you. Now has a better idea of what chapter wave is about.
@DrPhysicsA
11 жыл бұрын
All to do with harmonics. A trumpet and violin each playing middle C will produce the same fundamental (256 Hz). But they produce different harmonics each with different ampltudes. The C will be dominant but the harmonics affect the overall tonet. if harmonics were of the same strength as the fundamental you would hear a chord. But they are much less so you hear a different tone. Some composers try to achieve a similar effect with one dominant instrument and others playing harmonics at pppp.
@bigrockets
4 жыл бұрын
most excellent presentation on waves, angles of incidence , refraction and reflections. Well done!!!
@DrPhysicsA
12 жыл бұрын
I really couldn't improve on the excellent lecture given by Prof Walter Lewin of MIT on this. Search for "Walter Lewin - 8.02" and you should get to his lecture course 8.02. Go to lecture 6 which covers high voltage breakdown and sparks.
@DrPhysicsA
11 жыл бұрын
Think of it in terms of photons. The energy of a photon E = hf (where h is Planck's constant and f is frequency of the light). If f were to change then there would be a change in energy. Where would the energy gain/loss arise?
@DrPhysicsA
12 жыл бұрын
It's all down to quantum effects. Low energy photons (visible light/UV) tend to give up all their energy to an electron. Higher energy photons (in the X ray region) can show the Compton effect whereby they do give up only part of their energy to the electron and then recoil with lower energy (and lower frequency). Very high energy photons can give rise to pair production (eg electron-positron).
@SkiGav
11 жыл бұрын
Mate, ur the absolute best! love your videos and i really really appreciate what you're doing for everyone out there!
@Verbalbangz
12 жыл бұрын
By playing these over and over in my sleep i hope to remember it
@DrPhysicsA
11 жыл бұрын
To you and all sitting the exam today, all good wishes.
@0113slimshady
11 жыл бұрын
Why don't I have a teacher like you! Thanks soo much! :)
@DrPhysicsA
12 жыл бұрын
Are there any particular issues you want covered?
@DrPhysicsA
11 жыл бұрын
And you could then express the half a wavelength in terms of radians (ie pi in this case).
@DrPhysicsA
11 жыл бұрын
I assume you mean something like a sound wave. A sound wave propagates as a longitudinal wave by causing oscillations in the air which unlike transverse waves results in air molecules being pushed back and forth creating areas of compressed air and rarefied air which are constantly changing.
@DrPhysicsA
11 жыл бұрын
Yes. At 11:55 I is proportional to 1/r^2 because P/4pi is a constant
@DrPhysicsA
11 жыл бұрын
I'm not sure. I make videos of A level subjects which should cover material in most syllabuses. But I'm not sufficiently aware of the material required for each individual exam board.
@DrPhysicsA
11 жыл бұрын
It's what happens if you throw 2 stones into a pond and watch the waves overlap (they may not be the same amplitude). You still get superposition but since they are of different magnitude you dont get total destructive interference.
@mattbike1
12 жыл бұрын
I managed to get a B in my mock for this, and ive been told i should expect a D/E. Thank you, ill keep trying for the A :)
@LucisFerre1
10 жыл бұрын
I find these videos to be completely addictive.
@DrPhysicsA
11 жыл бұрын
The velocity of a EM wave changes in different media. Since frequency remains the same the wavelength must change. A beam of light which could be regarded as a wave, has millions of photons. But if you are talking about representing subatomic particles as waves rather than particles then the particle is itself also a wave. Each particle is also its own wave.
@Adsabs12
11 жыл бұрын
i do take chemistry, yes the exam was unusual, yet, after i saw the physics exam i changed my mind, it's considered very easy in comparison!
@DrPhysicsA
12 жыл бұрын
Thanks. Do you mean at 7:09? If so, I have put a text comment on the video to say that it should be r squared.
@DrPhysicsA
11 жыл бұрын
Not sure I can do that at present, but I see from the internet that there are ways of downloading from KZitem for later viewing in the style of a podcast.
@marianthejuniorscientist6422
6 жыл бұрын
Really great resource for students as well as teacher ...
@DrPhysicsA
11 жыл бұрын
n is an integer 1, 2, 3 etc. It is the number of the fringe (ie bright spot) from the centre. You can have as many fringes as can be fitted into the formula nλ/d = sin ϴ. ϴ can never be more than 90 degrees.
@DrPhysicsA
11 жыл бұрын
I'm not sure which exam board you are doing but my A Level Physics playlist should cover all the material you are likely to need. I also have a series of 7 videos on electromagnetic waves in the Electricty and Magentism playlist starting with "What is light?" but that is likely to be more advanced than you will need.
@DrPhysicsA
11 жыл бұрын
The gap thro which the wave passes has to be broadly the same size as the wavelength. That's why sound "diffracts" through a door but light doesn't.
@niharikags6129
11 жыл бұрын
Very Well Explained!! You are very good teacher! You have made difficult concepts much easier to understand! Hats off! Thank you!
@AlchemistOfNirnroot
9 жыл бұрын
Why are you saying integral? Did you mean integer? ~ 26:45
@shreyakc9618
7 жыл бұрын
he meant fringe
@wateen914
7 жыл бұрын
Thank you so much it was really helpful, took few hours to watch this video with countless pauses but it worth it.
@fernandrasta4786
8 жыл бұрын
Your channel is fantastic, thx you so much ... I am watching them all
@DrPhysicsA
12 жыл бұрын
I don't think polarisers need to be used. See my video on Atomic Structure - A Level Physics where I describe how lasers work near the end.
@razieh9
11 жыл бұрын
Sorry, but I am just so amazed at your ability to draw straight lines and 90 degree angles so perfectly! I am so bad at drawing diagrams free hand
@khuzaimahsaqib692
7 жыл бұрын
thank you sir i have learnt much more in these 36 min
@bq1499
11 жыл бұрын
You're a GENIUS! You have helped me understand things I thought were impossible to understand. :D If you have time, I hope you start to go through Exam papers one by one to give us a more fundamental idea of everything in its application. Edexcel Papers and so forth. Once again thank you very much. :)
@jzhen92
11 жыл бұрын
Life just became more simple after this video! This guy is my glitch to pass physics this year :P
@DrPhysicsA
11 жыл бұрын
Well it probably depends on the syllabus you are studying. But if your teacher didn't cover it in your course then its probably not in your syllabus. Can you check with any of your fellow students or teacher?
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