From: SFPhysics@aol.com
Date: Thu Aug 14 2003 - 11:58:16 PDT
From: SFPhysics@aol.com Message-ID: <99.3bc983d3.2c6d35c8@aol.com> Date: Thu, 14 Aug 2003 14:58:16 EDT Subject: Old B&W TV (Big Bang Echo)
<<
> Subject: an old black and white tv
> From: "Malcolm McClain" <mbmcclain@msn.com>
> Date: Wed, 13 Aug 2003 14:36:11 -0700
> Greetings,
> I have two questions in regards to a (black and white) tv. First, is it =
> true that the static we obsereve comes from the big bang? Second, when I=
> put a magnet to the screen does it bend toward the positive pole and awa=
> y from the negative? Istn't there a beam of electrons being shot at the =
> screen?
> Thank you for your help.
> L8R,
> Malcolm
>>
Hello Malcolm:
The "snow," random radio white noise, you see on a television is mostly from
background radio waves generated naturally from many "local" sources. The Sun
and Jupiter are the greatest sources of radio energy in the solar system.
Electrical discharges of lightening on Earth is another major contributor.
Power lines and other man made sources also show up. Televisions receive the
radio frequency energy up to the Ultra High Frequency (named at a time before more
modern technology) which tops out at about 800 MHz (MegaHertz). The echo
noise from the Big Bang is higher yet into the GigaHertz and an ordinary
television would likely yield little from the lingering universal echo. A second
point is that the echo is very low in intensity and only very sensitive receivers
can detect it. A television sensitivity in measured in many microVolts from
the antenna and the echo signal is much less in amplitude.
The television CRT, cathode ray tube, has been around a long time. Electrons
are the "cathode rays" that are accelerated out of a "gun" in the end of the
evacuated tube. The bulge in the back of most sets is to protect the gun
area. The negatively charged electrons are focused by the gun into a thin beam
which travels toward the positively charged front of the tube where the
"phosphors" are. The old black and white set used a mixture of substances that would
glow white when struck by the beam. The beam spot is swept across and up and
down in a square pattern to "paint" the screen front. Once the electrons have
hit the phosphors and made them glow, they are drawn out through the highly
charged (many thousands of Volts) "anode" connection on the tube front.
While some CRTs used electrostatic attraction/repulsion to move the beam
spot, the majority of TVs, computer monitors, etc., use electromagnets placed
forward of the gun assembly. Electrons or any particle with a charge will have a
curved path in a magnetic field. What you see when a magnet is placed near
the face of a CRT is the electrons curving while passing through a magnetic
field. The direction of curve is determined by the "right hand rule" which states
that the forefinger of the right hand points from N to S in the field, the
middle finger at right angle points in the direction of the electron flow, and
the thumb pointing up will be in the direction of the electron curve path.
I hope that answers your questions.
Regards to all Pinhole Listers,
Al Sefl
Who's so old he walks a curved path without being near a magnetic field...
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