Introduction to the doppler effect | Mechanical waves and sound | Physics | Khan Academy

[@francislin9575]

First time I watched this video was 7 years ago when I was in elementary school trying to learn physics. Physics looked so fascinating to me back then. Now I am watching this as a college freshman studying sociology while learning physics as a requirement for science classes. What a strange cycle.

[@blacksunnydays]

Life man..... hope you are doing what your passion is !

[@KoltonBostrom]

Elementary school for 7 years and then college?

[@francislin9575]

@@blacksunnydays Just graduated in May with a bachelor of science in Data Science and minor in Sociology. Lol. Life indeed. 🤣

[@StagnantMizu]

@@francislin9575 good stuff, gl in life!

[@niasomin]

Hubble observed that the further galaxies are from our point of observation in the universe, the faster they are moving away from us. To determine how fast they were moving away, he calculated the redshift of the light waves they emitted - more redshift, faster movement away. Redshift is essentially the same as the Doppler effect but for light - the wavelengths of light travelling away seem longer (more "red"). (shhh, I'm sure it's been said. just need to practice for tomorrow's exam :) )

[@RicardoTorres5]

Thank you so much for this video! I wasn't able to completely understand the Doppler Effect.Or well, I couldn't understand why people said that when an object is moving towards you, the waves get closer. Thanks to this video now I understood everything. Thank you!

[@DelijaZauvjek20]

For some that are confused about why the diagram to the right is different than the one to the left, imagine the left diagram being a pebble dropped into the pond that produces a ripple effect. Now, for the right diagram, imagine a bug that is drifting to the right. It is creating ripples in both directions of different frequencies :)

[@animeshsrivastava5597]

This is very well taught. Good Job !!

[@sagarkp1735]

La explicación más sensata y detallada que he recibido ... Gracias

[@nightmare4eVerr1]

I love you sal :D as hard it was in the book. U made it that much easier and understandable

[@megaelliott]

Well done Sal. I learned this in physics, but this is a much better explanation than my teacher gave.

[@Oocheri]

life saver. you make studying so much easier

[@dhirajkhanal5364]

I am extremely impressed! :) thanks!!

[@baloyinsuku5239]

Good vid... Who's here in 2021?

[@carlosescudero3161]

amazing i finally understand this. thank you

[@RasmusTranbjerg]

That's exactly what you experience when you sit at, maybe, a train crossing. Be careful not to sit too close. XD You sir are a genius, thanks..

[@boeing747200lr]

Sal, that was a mind-blowing explanation!!!!! Thanks :)

[@skippykipper101]

You explain this so well!! Thank you!

[@espen180]

I'm looking forward to your take on the relativistic EM doppler shift.

[@DMRook]

Yes it does actually. The Doppler Effect stretches out the wavelength of light until it reaches the red end of the spectrum, and eventually infrared; which means we can't see it. Which is why the sky is dark and we don't have constant light from stars.

[@Wizzy091]

Thank you for doing this! This really helped me with my Science coursework. (:

[@Chriscx]

Please help point out where im wrong :) I really do want to know With regards to all waves other than light. The doppler effect makes us ignore our understanding of basic relativity does it not? Isn't this much easier explained as, the car is moving forward towards us, as the wave is. Speed of wave initial + Speed of car = Speed of wave @ us. v=fλ, f=v/λ. Simply, since the wavelength is not changing (λ), but v (speed of the wave) is due to the speed of the car relative to us, we hear a higher frequency. Why does the doppler effect complete ignore this? Why does it make up a sort of compressing/stretching phenomenon that is exceptionally misleading, when by the time we learn the doppler effect, we've most likely already been educated on relativity, which I find explains what is happening sufficiently. Please point out where i'm wrong, this has been a very hard concept for me to understand because I believe it to be a fundamentally flawed explanation for SOUND waves.

[@sopehawley]

this explained everything thank you!

[@shahadjabiti1645]

Thank you that was useful

[@roseb2105]

can someone please help me out here it looks what this is trying to say is if the source advances 5 meters per second to the right that means that one second ( before 1 second) the source was 5 meters to the left and at this time created a wave surrounding it( circle) with the source ( in this case the dot being in the center) but then also kinda of moved along in its own wave that it created ?

[@buzzonme123]

this would be confusing to some, especially the part where ut seem to be that the wave increases as the source moves away from the observer

[@heyyitsmoi]

It actually does. It's the Doppler Effect for LIGHT. A source moving away is said to be Red-Shifted, and this notion was at the basis of E. Hubble's discovery in the 1920s that the Universe is constantly expanding.

[@sakshiagarwal4821]

Thankyou soo much sir you are great.

[@ikhan7077]

Sal Khan is the smartest guy in the room :)

[@aamiralikhan1081]

Awesome explaination Sallu bhai, loved it !!

[@kwuaa]

great video!!!!!!!!!!!

[@joih7]

Yes it does, as further away stars in the universe move faster away from us their light particle wavelenghts are altered in accordance to the Doppler effect and therefore change into infrared light which is not detectable by the human eye ("shifted out of the visual spectrum").

[@crosstowne59]

This was great. Thanks

[@roseb2105]

im confused about the picture on the right

[@SolacePiano]

Vote up if you know what Sheldon cosplayed as at Pennys halloween party ;)

[@takudzwatandara6932]

this was very helpful

[@deathnote123331]

so what the wave travles with the sorce? if so then nice demo

[@th3l0st3xpl0r3r]

At 3: 39 using pebble drop as an example for longitudinal waves(sound) is incorrect. Although I get the thought behind it; the fact is, longitudinal waves traverse in the same direction as the force applied whereas the waves created by a pebble drop traverse in a perpendicular direction to direction of the application of force.

[@johancool02]

This is the reason u hear things moving towards you more right? since the waves are closer to each other ?

[@extremerap]

thanks!

[@naomiiik_]

why is the wave 2 seconds bigger than the wave a second when you said that the wave moves outwards? I'm so confused...

[@muhammadizhan2741]

the dobpodopdler effect 9:36

[@ujjawaldugar1415]

I love ya Khan

[@maaheenyasin1003]

umm... I'm a bit confused in the video you said the source was moving 5m towards the right then why are we shifting the source towards the left plz explain me this why are we going back in time? and how can a crest be circular? isn't it like half of a sine wave?

[@danielkho70]

If the particle is moving to the right then a second ago it would be to the left of current position of the particle

[@danielkho70]

And the circular fronts represent wavefronts

[@adamumuhammed5070]

Good presentation

[@SamanthaSeltzer]

Why are we going back in time with the one on the right? I don't understand this

[@Ohhsoodead]

We aren't going back in time. The start point is irrelevant, it's the general direction of where the dot is travelling that's important. In this case the dot is travelling to the right, so standing to the right of the dots origin point will mean it's a higher frequency because the dot is travelling towards you, compared to standing on the left of the point of origin which means it's a lower wave frequency because the dot is travelling away from you, making the gaps in between the waves larger. I hope that makes sense. At least that's what I determined from watching the video. I'm new to this kind of stuff.

[@elsaj3662]

Im 11 and i love physics but i don't get to learn it in school in till grade 9

[@homamhassn4144]

Iam 13 and i loooove physics too Can we content We are similar

[@Saltukcan]

If you go faster then the crests you create you will trigger a sonic boom which means you go faster then sound.

[@SurinderSingh-cc8pk]

understood everything

[@yashmehan3944]

Nice Video, Sir! all of your videos are nice, so this comment doesn't make much sense, though. :) can you please tell about your hardware you used to make your videos? and what software is this?? please tell :)

[@SoumilSahu]

a wacom tablet and smoothdraw.

[@Trisador9]

Your idea is called the Olbers' paradox. The cause is a different one. Namly that the waves take time to reach us and some stars are going to be so far away that their light just hasnt reached us yet. Because this kind of proves the big bang theory what you read was probably Hoyle trying to find another explanation to save the steady-state idea...

[@Maloguh]

@seabm4 Not directly to do with doppler, but i'm assuming he meant "red shift" :) stars moving away appear to have a different color due to the doppler effect, because light has a wavelength as well. :D

[@artisticworld8189]

Ilu

[@clarencechoy2382]

You are better than my teacher

[@ejetzer]

It's linked to the relativistic Doppler effect.

[@Nodoybefore]

BIG BANG THEORY best show ever

[@norzafimizan5632]

I was expecting you to say "bye pitch, bye frequency". :( Good video, totally understandable

[@mohebmohi]

Somebody HELP!!! Why is the wavelenth constant, as we move away or toward, the frequency will change, why doesn't the wavelength change too ? where V=Wavelength x Frequency

[@setarehsaremi3265]

the frequency won't change it remains constant till end of it. it is one cycle per second and as you can see he draw the line according to this default that every second we have a pulse....

[@mohebmohi]

Setareh Saremi i know that he drawed it this way, but i want to understand it scientifically..i know C=Frequency multiplied by the wavelength, so there is a relation between both. | what is the logic explaning for this, what am i getting wrong..

[@StayGoldenBro]

thank godddddddddddd.

[@tupimir]

WHAT GUY!!

[@MustNotRead]

@GabrielFane "sonic boom", like Guile from Street Fighter 2?

[@Justanotherbirdd]

Celal şengörü daha iyi anlamak için burdayım

[@leylijohnson6656]

oh sal

[@eindor10]

0:02 think about TWOOO waves

[@sunnyv12345]

Red Shift has to do with the doppler effect

[@tonyjones771]

Ummm...ever heard of Doppler's redshift and blueshift?

[@homamhassn4144]

But why the sound disappear at the end if that was true the sound won't dissapper

[@juancastillo9066]

This beginning of the explanation is incorrect. The frequency of the waves should be increasing with respect to the observer we are moving to.

[@theflash9735]

Nope! YOU are the one who is *WRONG* , that frquency is for the first case not both the casese, it appears that you didnn't completely understand that . (I'm not trying to blame you or something by the way)

[@anushreeh6826]

Got confused....are there 2 cases??

[@rajatkumar35]

Actually in a way the Doppler effect suggested the big bang theory , so yes it does !

[@Rascal157]

Actually, you just heard that on the related Vsauce video.

[@Tspinnage]

why is he moving to the left and then saying that it moves to the right? the moving source of waves? sorry new to psychics

[@LifeOfASmiley]

The way he does is doing it could be a bit confusing. The best way I could explain is that he is looking at a source currently and looking at what it would have been doing in the past. He says it's moving to the right, but because it is moving to the right, it was to the left before the current moment he was observing the source. Not the best explanation, but hope it helps.

[@bhavyasrivastava3700]

Unable to understand anything

[@lowkeyleanin]

smth is wrong wid you then

[@jeyashanmugasamy574]

Who is here in 2022

[@Mutubeish]

i may have come here, thanks to the big bang theory lol

[@IowaEngineering]

@kjunaa

[@ShannonT_USMC]

This is a bit confusing and poorly constructed

[@AnuragPradhan101]

Unable to understand this video, why frequency is remaining constant..

[@oscarjuul3229]

The same amount of "wavetops" hit both persons, it's just the distance between them which changes.

[@dyutimoydan8752]

Abhi bhi samaj nahi aya kya ?

[@AnuragPradhan101]

@@dyutimoydan8752 Doesn’t matter now. I’m done with my graduation.

[@johancool02]

Nvm my last comment he just explained it in the video lol

[@Narsil1000]

It does, please learn your physics first.

[@Maddof_Erroz]

SHELDON COOPER

[@10101001111]

MH370

[@LanRous]

@schizophrenic123 it is not crap

[@WoahhItsBryan]

You stole my explanation.

[@HickeyHickeyMan1]

the most embarrassing comment ever

[@steppedunk]

really confusing

[@gauravkamath9569]

What confused you?

[@steppedunk]

i finally got it thanks to michel van biezen and his channel

[@SolacePiano]

Hahahahahaha

[@TeKNiQ50]

lmao!

[@romz11khan]

I dont understand a word he is saying

[@pragyadhungana6984]

You are really awful at making people understand

[@rockstarmunibala2835]

Nice

[@hamidaalmusallami8054]

Probably your brain isn’t good enough

[@takudzwatandara6932]

this was very helpful

[@IowaEngineering]

@kjunaa