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## Homework Statement

An electron in the beam of a typical television picture tube is accelerated through a potential difference of 2.0*10^4 V before it strikes the face of the tube. What is the energy of this electron, in electron volts, and what is its speed when it strikes the screen?

## Homework Equations

delta V = delta Ep/q

Ek=0.5mv^2

## The Attempt at a Solution

well, I used the first equation to find its electric potential energy, which is (2.0*10^4)*(1.6*10^-19), and that gives me 3.2*10^-15J

then since it's asking in eV, and 1eV = 1.6*10^-19J, i do (3.2*10^-15)/(1.6*10^-19), which gives me 2*10^4eV (exact number as we started).

I don't see anything wrong with the procedure but the answer is 2*10^-4eV. what did i do wrong?

as for speed: (im using my 2*10^4eV as the energy)

Ek=0.5mv^2, and energy in J is 3.2*10^-15J

so 3.2*10^-15 = 0.5 (9.11*10^-31)v^2

that gives me 8.4*10^7m/s, which is exactly the same as the answer.

therefore I'm assuming the answer key for the energy in eV is wrong, what do you think?