When to use De Broglie Equation  [ENDORSED]


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Isabella Sanzi 2E
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When to use De Broglie Equation

Postby Isabella Sanzi 2E » Tue Oct 17, 2017 10:02 pm

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
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Re: When to use De Broglie Equation  [ENDORSED]

Postby Emilie Hoffman 1E » Tue Oct 17, 2017 10:08 pm

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
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Re: When to use De Broglie Equation

Postby Elika Asis 3C » Wed Oct 18, 2017 10:49 am

^^^
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
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Re: When to use De Broglie Equation

Postby Varsha Sivaganesh 1A » Fri Oct 20, 2017 9:57 am

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
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Re: When to use De Broglie Equation

Postby Ishan Saha 1L » Fri Oct 20, 2017 10:06 am

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
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Re: When to use De Broglie Equation

Postby Sydney Briggs 1B » Fri Oct 20, 2017 1:14 pm

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
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Re: When to use De Broglie Equation

Postby Josh Moy 1H » Sun Oct 22, 2017 7:44 pm

Use when you have mass and velocity and need wavelength

Haocheng Zhang 2A
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Re: When to use De Broglie Equation

Postby Haocheng Zhang 2A » Sun Oct 22, 2017 8:25 pm

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
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Re: When to use De Broglie Equation

Postby Karan Singh Lecture 3 » Sun Oct 22, 2017 8:29 pm

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

Chem_Mod
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Re: When to use De Broglie Equation

Postby Chem_Mod » Mon Oct 23, 2017 1:22 pm

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
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Re: When to use De Broglie Equation

Postby Kai_Chiu 1F » Sat Oct 28, 2017 10:39 am

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

nanditasundarapandian1D
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Re: When to use De Broglie Equation

Postby nanditasundarapandian1D » Sat Oct 28, 2017 12:46 pm

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


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