Ratio kinetic energy of alpha particle / kinetic energy of proton

[385sk117]

Homework Statement

A photon and alpha particle are accelerated from rest through the same potential difference.
After acceleration what is the ratio kinetic energy of alpha particle / kinetic energy of proton?

Homework Equations

I guess I have to use eV = 1/2mv^2

The Attempt at a Solution

I don't know what value have to be used in place of e in equation eV = 1/2mv^2
the mass of alpha particle is approximately 4 times of photon and that's all i know
I guessed the answer as 4 but the answer was 2
I think there is something to do with the velocity of alpha particle and photon but I'm stucked can not think of anything..

 

[ImAnEngineer]

An alfa particle has two protons, so that's twice the charge of one proton.

 

[385sk117]

Thanks a lot! So i didnt have to know the exact charges but the ratio