## How to know which equation to use

$\lambda=\frac{h}{p}$

904914037
Posts: 65
Joined: Wed Sep 18, 2019 12:16 am

### How to know which equation to use

When trying to find the velocity of an object, how do you know whether to use the equation v=c/(wavelength) or v=h/(mass x wavelength)?

Diana_Diep2I
Posts: 130
Joined: Sat Aug 17, 2019 12:17 am

### Re: How to know which equation to use

We can only use v=c/wavelength if you're trying to find the frequency of light

Diana_Diep2I
Posts: 130
Joined: Sat Aug 17, 2019 12:17 am

### Re: How to know which equation to use

And isn't it also whatever value is given? Is there an example problem that you have?

Brittany Tran 3I
Posts: 50
Joined: Sat Jul 20, 2019 12:16 am

### Re: How to know which equation to use

the equation v=c/wavelength is used to find frequency, not velocity. you can use v=h/(mass*wavelength) to find velocity, depending on the specific question

Minh Ngo 4G
Posts: 137
Joined: Thu Jul 25, 2019 12:17 am

### Re: How to know which equation to use

I think you get confused "v" of velocity and "v" of frequency. But i guess it depends on the info given to you???

904914037
Posts: 65
Joined: Wed Sep 18, 2019 12:16 am

### Re: How to know which equation to use

Yes, I forgot that "V" and "v" represent different variables! Thank you for the clarification, it makes sense now!

BeylemZ-1B
Posts: 95
Joined: Thu Jul 25, 2019 12:17 am

### Re: How to know which equation to use

904914037 wrote:When trying to find the velocity of an object, how do you know whether to use the equation v=c/(wavelength) or v=h/(mass x wavelength)?

the "v" is not in reference to velocity as it would be in Physics. the "v" is the frequency of the light!! definitely a distinction that needs to be made.

505106414
Posts: 55
Joined: Wed Sep 18, 2019 12:17 am

### Re: How to know which equation to use

What is a real-world application of this equation?

Jocelyn Thorp 1A
Posts: 103
Joined: Wed Sep 18, 2019 12:20 am

### Re: How to know which equation to use

505106414 wrote:What is a real-world application of this equation?

the v for frequency is actually nu (fun fact), and this is used to calculate wavelength, where c=lambda*v.

Brynne Burrows 3K
Posts: 52
Joined: Thu Jul 25, 2019 12:16 am

### Re: How to know which equation to use

Both of those equations are referring to v as frequency instead of velocity, but you can use velocity in the equation E=1/2Me*Ve.