## Equations

$c=\lambda v$

Hannah Faris 1C
Posts: 34
Joined: Fri Sep 28, 2018 12:18 am

### Equations

Hi, I’m a little bit confused about the use of equations.

Which equations do we use for solving for particles, and which are for light? I need some help getting them straightened out in my head.

Thanks!

Tiffany_Cacy_3D
Posts: 70
Joined: Fri Sep 28, 2018 12:24 am

### Re: Equations

We went over this a little bit in our discussion week so hopefully this will help.

1)Energy of a photon: E=hv and c=v(lambda) -These are commonly used in questions concerning the photoelectric effect.These are used for photons only.

2) De Broglie's Equation: lambda=h/p(momentum) -Although this also has an equation that solves for wavelength it is not used for photons but for particles. Usually you know when to use this equation because it will give you variables such as mass and volume. If these are not given it is a good indicator that you do not need to use this equation.

3) Photoelectric Effect: E=hv-(work function)= 0.5mv(squared) -This equation is also used when working with photons.

Our TA advised us to pick the equations we use based on the information given in the problems. Usually you only use De Broglie's if mass or volume are involved.

amogha_koka3I
Posts: 62
Joined: Fri Sep 28, 2018 12:24 am

### Re: Equations

Will we be required to know how to derive De Broglie's Equation?

Amy Dinh 1A
Posts: 62
Joined: Fri Sep 28, 2018 12:23 am

### Re: Equations

amogha_koka3I wrote:Will we be required to know how to derive De Broglie's Equation?

No, De Broglie's Equation is given on the "Constants and Equation" page, but it is not labeled as De Broglie's equation.

RoopshaChatterjee 1G
Posts: 30
Joined: Fri Sep 28, 2018 12:17 am

### Re: Equations

With all the equations in this section how do we know when a v is frequency and when it represents velocity?

Nathan Mariano 2G
Posts: 68
Joined: Fri Sep 28, 2018 12:29 am

### Re: Equations

RoopshaChatterjee 1G wrote:With all the equations in this section how do we know when a v is frequency and when it represents velocity?

In response to your question, there are different notations for frequency and velocity. Frequency is denoted with the Greek letter nu, while velocity is denoted with the letter v.

Posts: 73
Joined: Fri Sep 28, 2018 12:15 am

### Re: Equations

I also heard that the test is going to be more conceptual, so I think as long as you know how the equations relate to each other as well as what the variable/parameters represent, you should be fine for the most part.

Yixiao Hu 3C
Posts: 45
Joined: Fri Sep 28, 2018 12:19 am

### Re: Equations

1.hv=c
2.lamthum=h/p=h/mv
3.E-work function=1/2mv2