the speed of electron

Tom Roberts wrote: double precision wrote: Tom Roberts wrote:
big magician wrote:
does anyone knows the speed of the accelerated
deviated electrons in a crt?
The accelerating voltage of a typical CRT is about 15 kV, so the kinetic
energy of an electron when it hits the screen is about 15 keV; it
therefore has v/c ~ 0.03.

would you minde being more specific on
how you came up with tha 0.03

I see I made a mistake. Sorry.

I use units with c=1: keV for energy, keV/c^2 for mass, and keV/c for
momentum (since c=1 these distinctions are notational only).

KE = 15 keV
m = 511 keV/c^2
E = m + KE = 526 keV
P = sqrt(E^2 - m^2) = 125 keV/c
beta = v/c = P/E = 0.24

No ANGULAR momentum in there, anywhere, Tom? Duh, ```Brian.

So this is more relativistic than I originally said, but not enormously
so. gamma-1 is a typical measure of how large relativistic effects are,
and that is 0.029 or ~3%. To obtain good crisp images across the face of
a CRT (especially position being linearly related to the signal voltage)
I suspect they must be taken into account in the design.

As others have pointed out, bigger screens use larger voltages.
Increasing to 25 kV only increases v/c to 0.30 and gamma-1 to ~5%.

Tom Roberts
the speed of electron.