We also have the frequency of the listener so this formula all of this formula is actually equal to the frequency of the listener okay so ladies and gentlemen the listener should be able to register the frequency as a result of the source okay very much important ladies and gentlemen so that so that means the source must emit a sound which the listener must register that sound and what do they register ladies and gentlemen we are talking about the frequencies.
Okay so that means the sound emitted by the source will release certain amount of frequency which is going to be registered by the listener or an observer okay and again it could be a detector which detects sound very very much important ladies and gentlemen that you understand this formula.
Okay so now let's have a look at the information that were given and then from there try to um you know substitute into the formula and proceed with our calculations ladies and gentlemen it's very much important that you fully understand exactly what the question wants you to calculate okay remember they want you to calculate the frequency of the sound okay.
The frequency of the sound that the observer hears most importantly while that train is approaching the observer okay taking into account that the speed of velocity of the sound in air is a 340 meters per second okay very very much important ladies and gentlemen so that v and that v is the same okay in terms of magnitude or in terms of the value okay.
So ladies and gentlemen can we do it the primary way where we say a given data so we know ladies and gentlemen we've got a frequency let me just say in that order to say frequency of the listener it's equals two then you're able to put a question mark over there because that is exactly what the question wants you to calculate okay very very much important ladies and gentlemen so now what is that v over there okay then we know ladies and gentlemen excuse me we know v um v refers to the speed of sound in air and is given as 340 a meters per second okay very very much important ladies and gentlemen.
That you ride the units for speed or velocity okay so ladies and gentlemen remember this v is the same v there and there okay so now what is the v of the listener ladies and gentlemen what is the velocity of the listener or velocity of a the observer or the velocity of a detector ladies and gentlemen it doesn't really matter whether it's a detector whether it's an observer whether it's a listener in this case i'm just saying all of this so that you are aware that it could be a an observer it could be a listener it could be a detector or whatever it could be okay.
So we're just trying to explore all the information relevant to this chapter so ladies and gentlemen we know the velocity of the listener is zero meters per second okay why it's because on the statement they said an observer standing on the platform so for that reason it means a the velocity of the listener is zero meters per second because he is standing okay ladies and gentlemen let's now talk about velocity of the source okay v of the source ladies and gentlemen it's very much important that you remember that there we talk about the velocity which is measured in meters per second.
Okay so what is the velocity of the source so a source could be an ambulance a source could be a police vein a source could be a train in this case a source could be any moving car a you know emitting sound a source could be anything approaching the listener so that means ladies and gentlemen you should be able to find out from the statement which one is the listener and which one is the source okay very much important ladies and gentlemen that you are able to differentiate between the two okay so velocity of the source is equals to 20 meters per second very very much important ladies and gentlemen a constant speed of 20 meters per second is the speed at which the source is approaching the observer or the listener okay.
Ladies and gentlemen what else have we got on the formula remember ladies and gentlemen i'm not referring or asking myself what is it that were given from the statement but instead i'm saying what does the formula have and then from there based on what the formula has i'm just checking through each and every quantity to see if we are given the magnitude of that particular quantity okay so now let's talk about a you know frequency of the source okay frequency of the source it's equals two ladies and gentlemen they've just said frequency of the source it's four five eight heads okay four five eight Hz...
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