Date: Mon, 23 May 2011 11:48:01

Author: Zani, Gerald

Subject: Re: Polarization, Brewster's Angle, Green Laser Better?

Post:

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Why use a laser at all?

You can use an un-polarized light source because it gets polarized upon
reflection at the Brewster angle from the water surface.

Do it with white light from a tungsten filament.

I use a ray projector from the black board optics kit. - Jerry



On Mon, May 23, 2011 at 11:22 AM, Bill Norwood wrote:

> Hi Taplers,
>
>
>
> I am making progress on our polarization & Brewster=92s angle experiment.
>
> But, here is another question:
>
>
>
> Given that we must stay with class II lasers, not illegal laser pointers =
at
> 5mw etc, in the student labs we have stuck with 1mw class 2 red diode las=
ers
> (now $400 ea at Edmund Optics for their new replacement model) for the
> polarization lab. And, given that we need all the laser intensity we can =
get
> when taking measurements near Brewster=92s angle might we possibly be bet=
ter
> off with a green laser? We are using a vernier light sensor with Logger-P=
ro
> software. I understand that green lasers are more effective than red in
> laser pointers because the eye is more sensitive to green light. But migh=
t
> the Vernier light sensor be more sensitive to green light?
>
>
>
> Come to think of it, a critical part of the experiment is being able to S=
EE
> the laser beam at very low light levels, in order to align the beam with =
the
> light sensor, when working very close to Brewster=92s angle, so maybe gre=
en
> would be better!
>
>
>
> Anybody got a sense as to how much more visible green is to the human eye=
?
> Would half the power seem just as bright as a red laser, for example?
>
>
>
> Thanks for any guidance.
>
>
>
> Bill Norwood
>
> Elementary Labs,
>
> U of MD at College Park
>



--=20
Gerald Zani
Demonstration Manager
Physics
Brown University
(401) 863-3964

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Why use a laser at all?You can use an un-polarized light source bec=
ause it gets polarized upon reflection at the Brewster angle from the water=
surface.Do it with white light from a tungsten filament.

I use a ray projector from the black board optics kit.=A0 - JerryOn Mon, May 23, 2011 at 11:22 AM, Bill Nor=
wood .edu> wrote:

Hi Tap=
lers,

=A0I am making progress on =
our polarization & Brewster=92s angle experiment.

But, here is another question:<=
p class=3D"MsoNormal">=A0Given that we must stay with class II lasers, not illegal laser p=
ointers at 5mw etc, in the student labs we have stuck with 1mw class 2 red =
diode lasers (now $400 ea at Edmund Optics for their new replacement model)=
for the polarization lab. And, given that we need all the laser intensity =
we can get when taking measurements near Brewster=92s angle might we possib=
ly be better off with a green laser? We are using a vernier light sensor wi=
th Logger-Pro software. I understand that green lasers are more effective t=
han red in laser pointers because the eye is more sensitive to green light.=
But might the Vernier light sensor be more sensitive to green light?

=A0Come to think of it, a c=
ritical part of the experiment is being able to SEE the laser beam at very =
low light levels, in order to align the beam with the light sensor, when wo=
rking very close to Brewster=92s angle, so maybe green would be better!

=A0Anybody got a sense as t=
o how much more visible green is to the human eye? Would half the power see=
m just as bright as a red laser, for example?

=A0Thanks for any guidance.=
=A0

Bill NorwoodElementary Labs,U of MD at College Park=


-- Gerald ZaniDe=
monstration ManagerPhysicsBrown University(401) 863-3964

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