physics question; de Broglie wavelength

[Kenazo]

I'm busy studying for my physics exam on friday, and I can get most of the questions but this one stumps me;

In a TV tube the electrons are accelerated from rest through a potential difference, V. Just before an electron strikes the screen, its de Broglie wavelength is 1.0x10^-11 m. What is V?

ok, so I know how to do de Broglie wavelength, (wavelength=Planck's constant (H)/ Momentum p) but how do i figure out the voltage?

 

[goodoptics]

nm.

 

[Haircut]

As you are accelerating the electron through a p.d. the energy gained is equal to the number of volts.
I.e. an electron accelerated through 1000V will have an energy of 1000eV

E=h*freq = hc/wavelength

In this case wavelength =1*10^-11
so E=1.989 * 10^-14 J

1ev=1.6*10^-19 J, so Voltage is 1.989*10^-14 / 1.6*10^-19 = 124312V

 

[Kenazo]

Thanks a lot Haircut! Now i should be able to get my A.