Re: basic question about light
- From: Llanzlan Klazmon the 15th <Klazmon@xxxxxxxxxxxxxxxx>
- Date: 9 Feb 2007 13:53:17 +1300
"Aaron" <anodide@xxxxxxxxxxx> wrote in news:1170935386.284334.127400
@l53g2000cwa.googlegroups.com:
Posters here seem to have all sorts of backgrounds, and I'm figuring
that asking a rather simple question is an OK thing to do. So here
goes.
(1) I point a laser straight up.
(2) I do not see any laser light from sitting next to it, my gave
directed perpendicular.
Try it with a green laser pointer. Ordinary dry air will give enough
scatter for even a 5mw beam to be clearly visible. No smoke needed. These
are often used as teaching tools for pointing out stars. The beam can be
seen for sufficent distance to clearly indicate which star is being
referred to. BTW if you try this, do not until any circumstances direct a
laser towards an aircraft. You are likely to get the dept of homeland
idiocy to deal with.
http://www.skypointer.net/
(3) I blow smoke at the laster light
(4) I see the laster beam.
I am trying to understant some of the basics of light here.
The laser uses some gas to generate photons and get them going in the
same direction.
The smoke reflects some of the photon into different directions than
they started.
QUESTION #1: What does it mean for a molecule of gas to "reflect the
laster light" ?
A molecule is like a giant wall to a photon and it just bounces off
it.
When the ligh changes direction, it still goes at light speed.
Did the molecule have to give up any energy to allow this?
QUESTION #2: I see the light because photons go into my eyes.
I undertand that optic nerves respond to photons.
So, the photon must hit the optic nerve.
No exactly. It hits a cell in the retina, either a rod cell or cone cell.
These cells contain pigments which when excited by a photon indirectly
cause their host cell to generate an electrical pulse on the cell membrane
which gets picked up by the optic nerve. The rod cells are broadband in
their response but don't work so well in very bright daytime light as the
pigment they use (a type of rhodopsin) breaks down faster than it can be
replaced. In dim light conditions they come into their own. When you hear
talk of your eyes being 'dark adapted', a large part of that is the rod
cells building up the quantity of rhodopsin to levels where the quantum
efficiency of light detection is much improved (Of course the pupil opens
to maximum aperture which also helps). The other type of cell, the cone
cells come in three different types which are sensitive to more narrow but
overlapping bands within in the visual range. Their combined response
provides the sensation of color.
http://en.wikipedia.org/wiki/Rhodopsin
What happens? Does the photon cease to exist at some point?
When it does cease to exist, does this amount to energy transfer which
ultimately results in electrical stimulation of my nerve?
http://en.wikipedia.org/wiki/Visual_system
Klazmon.
.
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- basic question about light
- From: Aaron
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