# Question #d5082

##### 1 Answer

Jan 10, 2017

The basis of the derivation is to equate two energy expressions:

#E = hnu = (hc)/lambda#

#E = mc^2#

Thus:

#mc^2 = (hc)/lambda#

#mc = h/lambda#

#lambda = h/(mc)#

To apply this equation to things moving at not the speed of light, but their own speed, de Broglie implicitly assumed that the moving object would have a measurable mass:

#=> color(blue)(lambda = h/(mv))#

That, however, restricts the application to things **with** mass. i.e. you ** cannot** use this equation for photons, but you can use it for electrons.

It does, however, say that things with considerable mass do have a wavelength... it is just immeasurably small. It gets reasonably large for quantum particles, like electrons and protons.