- 3

- 0

**[SOLVED] Finding KE when given de Broglie wavelength**

**1. Homework Statement**

What is the kinetic energy, in MeV, of a proton with a de Broglie wavelength of 10fm?

1 MeV = 10^6 eV

1 fm = 10^-15m

1 eV = 1.602 x 10^-19 J

h = 6.63 x 10^-34 Js

wavelength = 10 x 10^-15 m = 10^-5 nm

Mass proton = 1.673 x 10^-27 kg

**2. Homework Equations**

wavelength = h/mv

KE = (1/2)(m)(v^2)

**3. The Attempt at a Solution**

I feel like I did this right, but I still got the incorrect answer and I can't seem to notice what I did wrong.

v = (6.63 x 10^-34) / (10^-5)(1.673 x 10^-27) = .03962 m/s

K = .5(1.673 x 10^-27)(.03862^2) = 1.316 x 10^-30 J = 8.2 x 10^-12 eV

= 8.2 x 10^-18 MeV