When to use DeBroglie's equation [ENDORSED]

[Samidha Menon 1E]

I was a little bit confused on knowing when to use DeBroglie's equation. Sometimes, we are able to use (wavelength)=(c/v), but I've noticed that we can't do this all the time. Would anyone be able to explain to me how to know when it is appropriate to use which equation?

[Phillip Ma 1J]

Hi! You use Debroglie's equation when you are dealing with matter, which includes electrons, baseballs, etc. You use wavelength=c/v ONLY for photons. Hope this helps!

[405669838]

We use DeBroglie's equation when we are given speed/velocity, and we use c= wavelength x v when we are given frequency. This can be confusing because the symbols for frequency and speed/velocity look similar.

[Madison Rhynhart 3H]

Hi! DeBroglie's equation is meant (and only meant) to be used when dealing with physical matter like electrons, basketballs, baseballs, anything of that sort where as the equation wavelength = c/v is used for photons or light waves! This is because with DeBroglie's equation we can take into account velocity in terms of mass where as the latter equation takes in v as frequency of the wavelength and not the velocity of an object.

[Alex Luong 3H]

I also want to add something that can help you remember when to use DeBroglie's equation. In order to use it, you need to know the mass of the particle. Photons don't have mass (or at least I was told), so you can't use DeBroglie's equation with photons, and would use c = (wavelength)(frequency). Hope this helps!

[Meia Schram 1J]

Just like the others stated that De Broglie is for physical matters that have a mass!! If you can remember the mass part you should be golden because photons don't have a mass so the only way to find wavelength of frequency is with the speed of light equation, ONLY. But items like electrons, baseballs, or cars that have a definiable mass can be inputted into De Broglie's equation.

[Samantha Quevedo 2L]

Hello,
I wanted to add on to this because I am also a bit confused on when to use both but I believe when you are given mass and velocity then use can use DeBroglie's equation.

[AndreyCastellanos 3H]

We use DeBroglie's equation when we are given speed/velocity, and we use c= wavelength x v when we are given frequency

[MiaRosati3L]

Just like the others stated that De Broglie is for physical matters that have a mass!! If you can remember the mass part you should be golden because photons don't have a mass so the only way to find wavelength of frequency is with the speed of light equation, ONLY. But items like electrons, baseballs, or cars that have a definiable mass can be inputted into De Broglie's equation.

This was a very helpful explanation! To add on to this comment, the way I remember that De Broglie's equation is related to physical matter is because we learned in lecture about the 1923-1927 Davisson-Germer experiment. It was this experiment that confirmed Louis de Broglie's hypothesis of wave-particle duality. In the experiment, electrons were scattered by the surface of a crystal of nickel metal in crystal planes (so the atoms were regularly spaced). This generated a diffraction pattern with unexpected peaks and showed that particles (physical matter) can have wave patterns. Hope this helps! :)

[Luke Hatch 1G]

DeBroglie's equation is used when you are making a calculation for something with mass. c = (wavelength)(frequency) is used when doing calculations for photons, but photons are massless. When you need to do calculations for electrons, neutrons, protons, and other things with mass, you will use DeBroglie's equation
wavelength = h/p because that accounts for mass (p = mv).