v=frequency*wavelength .. when is velocity a constant?

[GomerPyle]

So when you are changing medium, frequency remains constant. I remember studying that in the same medium, velocity is constant and freq/wavelength may change? When do these apply? Light? Sound? Same medium? Just a little confused..thanks.

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[milski]

Any kind of waves.

The idea is that once a wave is made, its frequency cannot be changed. The other part is that for any given media you can convert between frequency and wavelength by using v=λf. In general, v is the same for all frequencies in the given media, although there is this thing called dispersion which makes it vary a bit for light. If the above is still a bit iffy, you're better of forgetting about dispersion at this point and treating v as a constant.

 

[yoyohomieg5432]

Any kind of waves.

The idea is that once a wave is made, its frequency cannot be changed. The other part is that for any given media you can convert between frequency and wavelength by using v=λf. In general, v is the same for all frequencies in the given media, although there is this thing called dispersion which makes it vary a bit for light. If the above is still a bit iffy, you're better of forgetting about dispersion at this point and treating v as a constant.

dispersion is a little much for the mcat i'd say.

as you said, transitioning between media, f remains constant. you know that the velocity can change in different media from the equation v=c/n, so if hte velocity changes and the frequency is constant, the wavelength must change, via the equation v=lambda*f

 

[milski]

dispersion is a little much for the mcat i'd say.

as you said, transitioning between media, f remains constant. you know that the velocity can change in different media from the equation v=c/n, so if hte velocity changes and the frequency is constant, the wavelength must change, via the equation v=lambda*f

I agree and I've never seen it on any practice AAMC material but it is on the list of topics for the physical sciences. I can't imagine it ever being worth more than a single question but if you want to be thorough, you need to have heard about it.

 

[adrakdavra]

I agree, but I have a Q
Why is V and T slope is a straight line , where as P and V in curved line . I know that P and V are inversely related, but why their slope is curved ?

Does that mean 1/X is always non linear , just like C=lamda X f, lamda = 1/f so it is an inverse relation with curved slop

 

[milski]

In short, because V=const * T, while P=const *1/V. Linear means proportional to the variable, not to one over the variable. As such, 1/x is never linear.

 

[adrakdavra]

so Inverse graphs are never linear

 

[milski]

so Inverse graphs are never linear

Yes.

 

[adrakdavra]

milski, what would you study if you have 19 days left for your exam and you not finishing on time in PHY and to improve timing and overall what would you do

 

[milski]

milski, what would you study if you have 19 days left for your exam and you not finishing on time in PHY and to improve timing and overall what would you do

I don't know if I'm the best person to give you advice on this. I never had problems with timing, so whatever I tell you is more of what I think should help vs. something that has been tried by me in practice.

First, why are running out of time, what is slowing you down? I would say that for a good number of problems basic manipulation of numbers in scientific notation is a must. You should be able to multiply two numbers and divide them by a third without losing time.

For both physics and chemistry - know the concepts cold. You should not have to spend time to think what an equivalence point is, what the kinetic and potential energy are in a given situation, etc, etc.

Try not to get bogged down in the details of the passage. You need to have an idea of what's described in it, not to understand every little detail of it.

If you get stuck on something - pick an answer, mark it and move on. If you have time, you can come back, if you don't - at least you have an answer there, with some chance to be right.

Also, be proficient in converting metric units. Meters to centimeters, etc. The linear ones are not too bad but square and cubic ones require some attention.

 

[GomerPyle]

So frequency is the same once a wave is made. If it changes medium, velocity changes (and therefore does wavelength). My question is, when you are in the same medium, the velocity is a constant (since you are not changing medium) and frequency cannot be changed as well? I know I read somewhere that velocity is constant for a medium.

 

[milski]

So frequency is the same once a wave is made. If it changes medium, velocity changes (and therefore does wavelength). My question is, when you are in the same medium, the velocity is a constant (since you are not changing medium) and frequency cannot be changed as well? I know I read somewhere that velocity is constant for a medium.

Yes, all of this is correct. Once the wave is made, the frequency is fixed. Once the wave with that frequency moves in a certain media, the velocity (for that media) is fixed too and you cannot change neither the frequency nor the velocity.

 

[adrakdavra]

Q 76Starting from a resting position at the left end of the railgun, the armature applies a constant force of 3.0 N to a projectile with a mass of 0.06 kg. How long will it take for the projectile to move 1.0 m?
. 0.02 s
. 0.04 s
. 0.20 s
. 0.40 s

Why is acc is not 10m/s2

 

[mehc012]

Q 76Starting from a resting position at the left end of the railgun, the armature applies a constant force of 3.0 N to a projectile with a mass of 0.06 kg. How long will it take for the projectile to move 1.0 m?
. 0.02 s
. 0.04 s
. 0.20 s
. 0.40 s

Why is acc is not 10m/s2

Answered in your other thread...but seriously, what possessed you to throw this in here? It's pretty rude, actually. Congratulations, I now slightly regret answering your question.

 

[adrakdavra]

Answered in your other thread...but seriously, what possessed you to throw this in here? It's pretty rude, actually. Congratulations, I now slightly regret answering your question.

take is easy , I put it in here for milski to see 😀

 

[mehc012]

take is easy , I put it in here for milski to see 😀

Exactly...threadjacking is, in general, unnecessary. I'm sure milski would see your Q in its own thread, and if you specifically wanted their advice, message them. No need to post completely irrelevant questions on a preexisting thread.

 

[milski]

Yes, I can see more than one thread, believe it or not. 😉 Posting in a separate thread is the best choice - everyone can see what it is about and not get sidetracked here.

Posting a thread is also a better idea than PM-ing me. I cannot promise how soon I can reply - maybe someone can help you quicker than me (like the case here). Not to mention, it is helpful to have the answer available to everyone.

 

[mehc012]

Yes, I can see more than one thread, believe it or not. 😉 Posting in a separate thread is the best choice - everyone can see what it is about and not get sidetracked here.

Posting a thread is also a better idea than PM-ing me. I cannot promise how soon I can reply - maybe someone can help you quicker than me (like the case here). Not to mention, it is helpful to have the answer available to everyone.

Haha, sorry milski...I was only putting that out there because they already made a separate thread, and still decided to post in here. I figured if they were adamant that it be you who answered (and STAT!) to the extent that making a thread wasn't enough, that was the next logical step!

 

[milski]

Haha, sorry milski...I was only putting that out there because they already made a separate thread, and still decided to post in here. I figured if they were adamant that it be you who answered (and STAT!) to the extent that making a thread wasn't enough, that was the next logical step!

No problem - I do answer PMs but I don't make any guarantees for quality of service. 🙂