Re: [ATM] No fringes

[Dale Eason <atmpob@yahoo.com>]

I doublt a geen LED is monochromatic enough.  I have
looked at them with a spectrograph and they have a
very broad spectrum.  I think I even remember some
red.

Dale Eason
--- Christopher Dalla Piazza <dalchri@hotmail.com>
wrote:

> I can't get fringes to appear on the interference
> test.
> 
> I am using a green LED which I assume is
> monochromatic enough.  There are a 
> few little specks of shellac which I left on my
> convex lens on purpose to 
> act as the shim and to also prevent glass on glass
> contact.
> 
> I have the concave reference R=185" facing me.  In
> front of that, I place 
> the convex, matching surface against it.  I know
> that the surfaces must be 
> getting close together because I have to overcome
> that vacuum force when I 
> try to separate them.
> 
> Next I just hold the LED next to my eye just like in
> the spit test and find 
> the effective radius of curvature when the light
> fills the lens.  This is 
> much close than 185" since the convex R=43" alters
> the focus, perhaps about 
> 60" away from the test stand.
> 
> Light fills the lens but no fringes.  I tried
> increasing the wedge to the 
> point that I could see a double image of the LED
> inside focus with no 
> change.
> 
> Do I need to create a pinhole or a slit for the LED?
>  Texereau just shows a 
> Neon lamp and a prism at the radius of curvature. 
> Is the orientation of the 
> air wedge important relative to my eye-source axis? 
> For example, if I place 
> the source to the right of my eye, does the thick
> part of the air wedge need 
> to be on the right and not the top or bottom?
> 
> Am I completely misinterpreting the illustration?  I
> wanted to avoid making 
> a diffuser but is that what needs to be done instead
> of being at the radius 
> of curvature?
> 
> Thanks again!
> 
>
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