Confused about equations

[Lizette Noriega 1H]

Hello,

This is a dumb question but I need clarification as to when you use certain equations since I always seem to mix them up. For instance, what kinds of problems indicate the use of the de Broglie equation (λ = h/mv) in contrast to the equations for wavelength (c= λv) and energy (E=hv)?

Thanks!

[Daniel Toscano 1L]

c= λv and E=hv apply to light (photons). I think De Broglie's (λ=h/(mv)) applies to particles (electrons), as do Heisenberg's and Schrodinger's equations.

[Michael Du 1E]

Adding to Daniel, you would use the De broglie equation when the velocity of some particle or so is given. The other equations have no correlation with velocity in it and you would think about using them when trying to solve for frequency or so.

[WesleyWu_1C]

The reason why you can only use c = λv for light is because pretty much everything else you need to find the wavelength for, has mass. For example, an electron has mass and mass is not considered in the c = λv. That's why if you want to find the wavelength (λ) for an electron you use the equation λ = h/p.

[Minh Ngo 4G]

Use deBrogile when you are given a mass

[Petrina Kan 2I]

According to the review session I went to, you would use c = λv only for light since it incorporates the speed of light. You would then use the DeBroglie equation for anything else, as these items will most likely be given with a mass in the problem. You can incorporate that with the E=hv equation because that one is not specific to light. Just make sure you don't use DeBroglie for light!

[Caitlin Ciardelli 3E]

only use c= λv when there is light involved!!!!
Whenever there is a mass mentioned or involved in the problem DO NOT USE THE LIGHT EQUATIONS!!! Instead use λ=h/(mv)

Whether or not mass is involved will determine which equation you will use

[AronCainBayot2K]

When mass is given, use De Broglie hence the "m" in the equation and not on the other light equations. Also the light equations given, usually relate to photons where as De Broglie relates to electrons.