janes (02/03/83)
A couple of questions:
Does anybody know the difference between REM, RAD, and RBE (relating to dosages
of radiation)?
Also, I've been told that there is no xray radiation from a picture tube, but
I did some calculations (which are further down) that show that the energy
for xray emission is there, and I can't see any reason why some wouldn't be
produced. The reason I'm wondering about this is that I found out that the
effects of chronic radiation exposure is much worse than acute (short)
exposures, even tho the total exposure is the same. Studies of effects of
about 500 mRem per year on animals are being done (this is the current
non-occupational threshold in Canada,US), and preliminary results seem to show
some long term damage.
The calculations follow, with signifigant parts marked with a ===>
About radiation from a tv/crt:
According to my calculations......
from
E=hv where h is Planck's constant = 6.626* 10^-27 erg-sec
v is frequency in cycles/sec
c=Yv where c is the speed of light = 2.9979*10^10 cm/sec
Y is (an excuse for lambda) the wavelength in cm
===> Y = hc/E = 1.986*10^-16 / E
Now, voltages in crt's are about 6000V (I could be wrong about this) giving
an electron 6000 eV (electron volts) or 6keV of energy, or 9.6132*10^-9 ergs
(1eV = 1.6022*10^-12 erg).
===> electrons in crt's have energies of 6keV or 9.6132*10^-9 erg
If this energy were to be converted to electro-mag radiation, it would have
a wavelength of 1.986*10^-16/9.6132*10^-9 = 2.066*10^-8 = 2.066 angstroms,
which is in the xray range.
===> 6keV photons have wavelengths of 2 angstroms, in the xray range.
Thats assuming all the kinetic energy is converted to em radiation.
>From what I've read, when the electron hits the end of the picture tube, it
would decelerate fast, producing a continuous spectrum of em rad., whose peak
is some what less than 6keV / 2 angstroms. How much less, I don't know - but
some lose all energy at once. So I think there should be some xrays. Anybody
got any figures? There are some element characteristic sharp peaks, but for
silicon and phosphorus, I suspect they are below xray range.
refs: 1st year physics text Mechanics, Berkeley series, for the constants.
Modern Physics and Quantum Mechanics p88-91 for xray stuff.
Oops, almost forgot -
Rob Janes
utzoo!utcsrgv!utcsstat!janes
U of Toronto Computing Services.caron (02/03/83)
DEL. q ~e
dkw (02/03/83)
I was around a physics dept two years ago which got word processors. Since there
was some concern about radiation we tried to measure radiation from the CRTs.
As far as we could tell there was no radiation. In other words what x-rays
there were were far below background levels.
David Wittenberg
{decvax, vax135, yale-comix}!brunix!dkw