Answer:
The first step in the solution is to calculate the kinetic energy of the electron:
KE=12mv2
E=12⋅9.11⋅10¯31kg⋅(2.5⋅106ms)2
E=2.84687⋅10¯17kg⋅m2s¯2 (I kept some guard digits)
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:
λ=hp
λ=h√2Em
=6.626⋅10¯34J⋅s√2⋅(2.84687⋅10¯17J)⋅(9.11⋅10¯31kg)
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.
