Equations for Light

[Autessa Anoosheh 3E]

I remember the professor said not to use an equation in regards to light, does anyone happen to know which equation that was?

[rachelcameron2E]

I'm not 100% sure, but he might have been referring to De Broglie's wavelength equation, λ = h/p. For this equation, you are solving the wavelength of an object by dividing Planck's constant, h, by momentum, p. Momentum = velocity x mass, so for this equation the particle/object you are calculating the wavelength for must have mass. Therefore, you cannot use this equation with light because it has no mass. I hope this is what you were looking for!

[Neelaj Das 3I]

He was talking about the De Broglie wavelength equation because this equation is meant for objects with mass. Photons are essentially massless and so its wavelength cannot be calculated using the De Broglie equation.

[Maddie Klee 3K]

Yes it was the De Broglie equation! That equation has to do with the mass of an object, but light's mass is so small (practically 0) that it wouldn't make sense to use this equation for light.

[Abby 2B]

Hi, I think it was the De Broglie equation he said not to use for light, because we have a lot of other equations we can use in regards to light, that this equation is not the best one.

[Mya_Chiarappa_2C]

Yes, it was the De Broglie equation because light does not have mass so it would have no momentum, because momentum is mass multiplied by velocity.