Doppler effect formula for observed frequency | Physics | Khan Academy

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Let's derive the formula for how the perceived frequency of a sound changes when its source is moving toward you. Created by Sal Khan.
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[@DivyashaktiGupta]

i'm pretty sure that someone who's watching a video on Doppler's effect would have reached a level that they know that distance is velocity times time. thank you for still explaining every little thing.

[@sameerahuja2853]

Divyashakti Gupta tumhara toh iit pkka 😂

[@rpw5083]

actually the integral of velocity

[@shakeelkhan9229]

write it is a very good condition

[@enverko]

Helped me get through mechanical waves, not just this video obviously! Thanks a lot!

[@ronycb7168]

The time period measured by the observer is the time taken between the first crest and second crest to reach the observer .. thanks, its an awsum derivation.

[@homestarhydon]

It's the same principle. Whether a car is moving towards you at 5 mph or you are moving towards the car at 5 mph is irrelevant, the waves act the same. So, if there is a problem where you are moving towards a stationary object at 5 mph, you can treat it as if the object is moving towards you at 5 mph as well. Or, (even though in relativity this isn't exactly the case) if you are moving towards something at 5 mph and it is moving towards you at 20 mph, you can treat it as if it's moving 25 mph

[@Starher0]

wow much better explanation than my teacher did thanks a lot

[@MysticMD]

Perfect! Thanks a million

[@orangeinfotainment620]

thank you!

[@sagarkp1735]

muchas gracias Sr. Sal. Esta es la conferencia más detallada e inclusiva a la que he asistido sobre este tema ...

[@EVismyname32]

You saved me from my Physics Periodic Test. TNX \m/

[@ProductionsRnR]

@theonlymoak, In that case it will depend on whether the police and the car being chased are in motion or not. If the car being chased moves faster than the police, then we should take the case where the source is stationary and the observer is moving, in that case, the relative frequency of the pulse emitted will increase. With this, the police will be able to find the relative position of the thief(chased car) by finding the distance.

[@SuperZkym]

A distance galaxy is moving away from us at a speed of 32,433,990 m/s. For hydrogen gas in this galaxy, calculate the wavelength (in nm) of the hydrogen alpha line as observed here on earth. Note: The wavelength emitted by hydrogen is measured in the first year physics lab (Expt. 24) to be 656.2 n

[@Ihatenicknames1]

Thank you so much :D this makes no sense in my textbook haha , but now I get it

[@vedareddy9330]

Brilliant. Thanks so much!

[@DavidJohnson-en9om]

Thank you so much.. you cleared my confusions and doubts...

[@ugursoydan8187]

thank you very much. you told very understandable

[@studentyo3077]

best video on this so far

[@corymorrison1993]

Great video!

[@hamidaalmusallami8054]

Is education everything?

[@PorkusSwordius]

great video. what software are you using to make it?

[@saumysharan2603]

thank u for solving my problem!!!!!!!

[@the_sophile]

Thanks a lot!

[@jackz5350]

Hey KA! I was using your iOS app to watch Doppler Effect videos, and I noticed that this video is missing from the playlist. It provides a bit of a logical gap, so it'd be helpful to update the app (and maybe even the website if it's missing from there too).

[@TheOnlyMoak]

so i have a question, hopefully someone can answer it. when police use radar guns they are applying the doppler effect. so when the wave hits the car what exactly happens to it? does it now take on the velocity of the car? without changing the velocity of the wave?

[@ronycb7168]

So the velocity of the wave does not change wrt stationary observer when the source moves..

[@Sebastian-vj7mw]

Pleas help me out: Why don‘t you add the velocity of the source to the velocity of the wave when you calculate T_0? (Is it because the observer is not moving in the medium and the wave velocity is given by the medium, but then this is just true for waves in a medium with the observer resting in it?)

[@upsteer1]

Salute Sir !!

[@dhirajkhanal5364]

Thumbs up!!

[@alext9067]

A light source is moving but the light is stationary. It's stationary because every wave generated radiates from the point in space where the light source is or was when the wave was generated. That wave widens thru space and it's center point is fixed. What is it fixed to? It's fixed to that universal coordinate system that is not supposed to exist. If this were not the case, Doppler shifting would not occur. Read more

[@madhusoodanshukla4277]

Who are you where do you work

[@ProductionsRnR]

Sorry. The relative frequency will decrease :p

[@kyubey8422]

Argh relying on Khan academy will make me fail my calculus physics class. Can't he do more difficult problems...

[@muhammedtai6282]

Kyubey btw, this is for AP physics 1, which is an algebra based course for highschool students ... so it makes sense that he's doing an easy problem.

[@moonlight-lq1hy]

Did u fail or did u pass?

[@VexxumGaming17]

l

[@Taylory0000]

I know he made this organization, but Sal is my least favorite person in these videos

[@Anas-nu7io]

mmmmmminus

[@TrickshotAgario]

who else has an agar.io tab open?!

[@sanskartewatia4320]

why did you mention it mate? just wasted 40 minutes of my life...

[@gauravkamat420]

🙄 Study Dude😭

[@ibrahimsaeed3677]

😡

[@ultimatepirate9589]

khan academy > physics book physics books should just be burnt because they are no longer very helpful

[@devindrarambo3293]

well technically is like he almost read every physics book and summarize it to give ya'll so you should be thankful for it :D

[@umapatki4068]

thank you so much