## When to use De Broglie Equation [ENDORSED]

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

Isabella Sanzi 2E
Posts: 54
Joined: Thu Jul 13, 2017 3:00 am

### When to use De Broglie Equation

I am just wondering under what circumstances that we can use the De Broglie equation. I understand that it solves for wavelength, but why use the de Broglie equation instead of another way to solve for wavelength? Does it simply depend on what information you are given? Also, why doesn't the equation apply to light?

Emilie Hoffman 1E
Posts: 55
Joined: Fri Sep 29, 2017 7:04 am

### Re: When to use De Broglie Equation  [ENDORSED]

The De Broglie equation equation outlines the idea that things that have rest mass (i.e. something that has weight) can behave like waves through having an oscillating way of moving (like basically they move back and forth over the line of their projected path) and thus wavelength. We can't use this to calculate the wavelength of light because light is by definition massless, which would make this equation perpetually zero. Thus the De Broglie equation is reserved for things that have mass, like electrons or baseballs.

Elika Asis 3C
Posts: 19
Joined: Fri Sep 29, 2017 7:07 am

### Re: When to use De Broglie Equation

^^^
To elaborate more, De Broglie's equation is typically used when the object's wavelength we are told to look for has mass. On the other hand, if we're dealing with massless particles like photons, we then use c=λν or E=hν. But in my discussion section, we were also told that we could use the c=λν for objects with mass, we just have to replace c (the speed of light) with velocity (not 100% that I worded that correctly though!)

Varsha Sivaganesh 1A
Posts: 51
Joined: Thu Jul 13, 2017 3:00 am

### Re: When to use De Broglie Equation

Also, when you need to use De Broglie the problem will give you mass and/or velocity, whereas if you were to use the other equation relating wavelength to frequency, they would give you the frequency of the photon.

Ishan Saha 1L
Posts: 60
Joined: Fri Sep 29, 2017 7:03 am

### Re: When to use De Broglie Equation

In addition to what everyone else has already said, it is important to note that DeBroglie's Eq is reserved for objects that have momentum. An objects momentum (p) is equal to its mass (m) times its velocity (v). This is why DeBroglie's equation has the notation λ=h/p, where λ is wavelength, h is Plank's Constant, and p is momentum.

Sydney Briggs 1B
Posts: 6
Joined: Fri Sep 29, 2017 7:03 am

### Re: When to use De Broglie Equation

To add onto this question, is there any way to connect finding the kinetic energy with the de Broglie equation? Since both contain mass, I wasn't sure if they could be used together.

Josh Moy 1H
Posts: 58
Joined: Thu Jul 13, 2017 3:00 am

### Re: When to use De Broglie Equation

Use when you have mass and velocity and need wavelength

Haocheng Zhang 2A
Posts: 52
Joined: Fri Sep 29, 2017 7:04 am

### Re: When to use De Broglie Equation

I think we can use de Broglie equation to find kinetic energy if we know the wavelength and either mass or velocity of the obeject.

Karan Singh Lecture 3
Posts: 23
Joined: Fri Sep 29, 2017 7:07 am

### Re: When to use De Broglie Equation

Debroglie is used for electrons, so one can find their wavelength.

Chem_Mod
Posts: 17997
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 418 times

### Re: When to use De Broglie Equation

Because for real particles you don't have another way to determine the wavelength. And it doesn't apply to photon since a photon doesn't have invariant mass.

Kai_Chiu 1F
Posts: 19
Joined: Fri Sep 29, 2017 7:03 am

### Re: When to use De Broglie Equation

The De Broglie Equation is used every time velocity and/or mass is given.

nanditasundarapandian1D
Posts: 21
Joined: Sat Jul 22, 2017 3:01 am

### Re: When to use De Broglie Equation

De Broglie's Equation is used to get a direct relationship between wavelength and momentum.