Converting de Broglie Wavelengths for Electrons at Different Voltages?

[xiphoid]

Homework Statement

What possibility can be the ratio of the de Broglie wavelengths for electrons accelerated through 50 volts and 200 volts, initially having same wavelengths?

Homework Equations

I have literally no idea how to convert volts into energy, here i somewhat i think,
Energy= Charge of electron * given volt.
if the above equation is correct then should i add the calculated energy to initial energy,
that will be initial energy+ calculated energy, the same way for both the potential differences given?

The Attempt at a Solution

 

[Simon Bridge]

1eV is the energy gained by one electron accelerated through a potential of 1V ... do everything in eV.
You only need the ratios ... so write out the formula for the debroglie wavelengths for each case and divide them out.