### De Broglie

Posted:

**Thu Oct 18, 2018 9:22 pm**When do you know when to use the De Broglie equation?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=18&t=34189

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Posted: **Thu Oct 18, 2018 9:22 pm**

When do you know when to use the De Broglie equation?

Posted: **Thu Oct 18, 2018 9:44 pm**

The DeBroglie equation only applies to particles with resting mass (for example electrons) that has momentum (p). You can't use this equation for something like light because light has no mass when at rest.

Posted: **Thu Oct 18, 2018 10:42 pm**

Just to add on, this equation can be used whenever you are given momentum (or mass and velocity), since h and c are constants. Then we can solve for wavelength if the particle has the momentum p and has wavelike properties with a wavelength lambda.

Posted: **Thu Oct 18, 2018 10:49 pm**

Also, p=mv. So wavelenght=h/p which is also wavelenght= h/mv.

Posted: **Thu Oct 18, 2018 11:08 pm**

On the homework problems, it some times gives you the velocity of a subatomic particle and you have to use the unit sheet (or google) in order to find the momentum (p) so that you can then move forward use De Broglie's equation.

Posted: **Sun Oct 21, 2018 10:46 pm**

When do you know to use the De Brogile equation? Will the questions always contain the words "De Brogile wavelength?"

Posted: **Sun Oct 21, 2018 11:19 pm**

The De Broglie equation indicated that the relationship between wavelength and momentum is inversely proportional. The equation is wavelength is equal to planck's constant divided by momentum( mass*velocity). You use to De Broglie equation to calculate de Broglie wavelength.

Posted: **Mon Oct 22, 2018 12:43 am**

The person I have my Peer Learning Sessions with said that most of the time the problems will tell you when to use it. However to identify it, it will ask you for the wavelength of something or the energy emitted as a result to the speed of wavelength (basically anything being questioned wavelengths).

Posted: **Thu Oct 25, 2018 10:17 pm**

Yeah,

if it gives you the speed of a subatomic particle, you can then use that to find the momentum by using the sheet of constants to find the mass of the particle. You generally use it when they ask for the wavelengthand give you speed or momentum.

if it gives you the speed of a subatomic particle, you can then use that to find the momentum by using the sheet of constants to find the mass of the particle. You generally use it when they ask for the wavelengthand give you speed or momentum.

Posted: **Sun Oct 28, 2018 9:19 pm**

de Broglie Equation Definition. λ = h/mv, where λ is wavelength, h is Planck's constant, m is the mass of a particle, moving at a velocity v. de Broglie suggested that particles can exhibit properties of waves.

Posted: **Sun Oct 28, 2018 9:20 pm**

You use it when the question asks you for a wavelength and the known object has a mass and velocity.

Posted: **Tue Oct 30, 2018 3:30 pm**

Use the De Broglie equation when you are trying to find the wavelength of a particle with momentum, such as an electron. You do not use the equation for light, since photons dp not have mass.

Posted: **Wed Oct 31, 2018 5:04 pm**

Summed up, use De Broglie when dealing with anything involving a rest mass and use the light equations when dealing with photons that have no resting mass.