# Uncertainty principle and tv picture tube

hey, Im really confused with this problem, i have tried to solve it for a while now but i cant seem to get it, i really dont even know where to start with it.

In a TV picture tube the accelerating voltage is V, and the electron beam passes through an aperture with a diameter of Delta_y and hits a screen which is a distance of x away.

What is the uncertainty in position of the point where the electrons strike the screen?
Use h for Planck's constant, m_e for the mass of an electron, and e for the magnitude of the charge on an electron.

any help would be great.

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Galileo
The idea is that the uncertainty in the position of the particle after it passes the aperture is $\Delta y$, which, if it is small enough, leads to an uncertainty in the momentum of the particle.