# What is the wavelength of an electron with a mass of 9.11 x 10^-31 kg and a speed of 2.5 x 10^6 m.s^-1.?

##### 1 Answer

1) The first step in the solution is to calculate the kinetic energy of the electron:

When I use this value just below, I will use J (for Joules).

2) Next, we will use the de Broglie equation to calculate the wavelength:

Now you can calculate final answer

Just to be sure about two things: (1) the unit on Planck's Constant is Joule-seconds, both are in the numerator and (2) there are three values following the radical in the denominator. All three of them are under the radical sign.