Just something I noticed a little while ago, and want to know why I keep getting this contradictory result.

From the de Broglie Equation,

lambda (here denoted as l) =h/mv, where m =mass, v =velocity and h = Planck's constant.

But frequency ( here denoted as f) = v/l

Therefore,

f = v/h/mv = mv^2/h

The energy of a wave is given by E= hf.

Therefore, E = hmv^h/h

Therefore, E =mv^2

Yet the energy should be equal to the kinetic energy of the particle, which is mv^2/2.

Why is it that I keep getting this answer?