Why does de Broglie's equation give wave velocity c for matter?

[Isaac0427]

De Broglie's postulate states that λ=h/p and ƒ=E/h. If you plug in E=pc, then you get λ=c/ƒ. Using the equation for wavelength λ=v/ƒ, I found that v=c, but this can't be true, because the matter waves would be traveling a c. What did I do wrong? Thanks!

 

[dextercioby]

E=pc holds only for massless particles. You have obtained that massless particles propagate at the speed of light. But that is obvious.

 

[Isaac0427]

E=pc holds only for massless particles. You have obtained that massless particles propagate at the speed of light. But that is obvious.

So do I need to factor in mc^2 too?

 

[Nugatory]

So do I need to factor in mc^2 too?

Yes. This will get you started: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/debrog2.html#c2

 

[Isaac0427]

Yes. This will get you started: http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/debrog2.html#c2

Thanks.