Monitors radiation question.

[jclose@potomac.ads.com (Jeff Close)]

   Date: Fri, 21 Jun 91 10:47-0000
   From: p2@porter.asl.dialnet.symbolics.com (Peter Paine)

   Does anyone have any feelings (Pan what are your measurement
   techniques?)  whether a monitor which is dimmed (L-machines/Lemo
   brightness turned down, G-machines Function-c-Refresh, MacIvory Radius
   screen saver stars, etc.) should emit less?

   Sitting at the focus of 4 screens that get used intermittantly during
   the day, I had hoped that dimming the screens would diminish emissions
   to insignificant levels. ie. radiation is caused by the tube beta rays
   striking the phosphore and producing weak X ray? which is absorbed by
   the lead glass?

   Or is the only effect a consequence of the 50/60 Hz mains induction
   field - such as is found in homes situated under power line cables?

   If the emissions are not related to the screen illumination intensity,
   ie. dimming completely, viewing as white text on black background, and
   at lowest intensity possibly - then should I be turning the monitor
   power off, except when in active use?

Speaking from dim memory as a former EE in years past, yes, intensity
DOES matter.  It's not just the em field from the operating frequency.
Brightness should make a difference as well as the amount of beam on
the screen (i.e., white on black vs. the reverse).  I doubt you can
reduce it to "insignificant" levels, though -- this is sort of like
saying "how much can I smoke and have it not affect me at all?"

So screen savers should also help, since it might as well be turned
off when you're not doing anything.  

Interestingly (sure sign of a boring comment to come), I have a PC
with a sound card at home, with a pair of small stereo speakers on
either side of the monitor.  The noise on the speakers varies with
distance from the monitor and depending on what's on the screen --
lots of bright windows cause more noise.

Jeff
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