[Laser] Chucks question continued

[Jim Moss]

Mike,
Looks like that is pretty cheap.
Looks like it is about 3nm resolution, and about 2 month delay to shipment.
You have to calibrate it yourself.
Might be interesting.  
Let us know how it goes.
Jim


Sent from my iPad

> On May 14, 2018, at 8:08 PM, Chuck Hast <wchast at gmail.com> wrote:
> 
> Jim,
> That did it. Now to go through it and get it into a stand alone little
> piece of
> say python code. A good exercise for me...
> 
> Then the larger angle was probably what was taking a bite out the numbers in
> the original calculation using the formula that you indicated was doing the
> approximation.
> 
> 
>> On Mon, May 14, 2018 at 8:21 PM, Jim Moss <n9jim-6 at pacbell.net> wrote:
>> 
>> Chuck,
>> It looks like we may have sin and tan issues here
>> 
>> Original cited article:
>> http://laserclassroom.com/products/measure-wavelength-laser-light/
>> 
>> The angle based on your data is arctan(627/1000) = 32.08771207 Degrees
>> That’s diffraction distance (X) / distance to target (L)
>> 
>> The grating equation is WL = d sin(32.08771207), d=1000/mm
>> Or 531.2 nM.  That matches your laser source.
>> 
>> Note that in your original cited article approximates sin = tan.
>> This is true when the angle is small, but introduces errors at larger
>> angles.
>> 
>> Here’s a calculator for the experiment: not using the approximation.
>> http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/gratcal.html
>> 
>> Jim
>> 
>> Sent from my iPad
>> 
>>> On May 14, 2018, at 5:40 PM, Jim Moss <n9jim-6 at pacbell.net> wrote:
>>> 
>>> Chuck,
>>> 
>>> After rereading, I think my statement on d is not correct. It may be as
>> simple as 1 mm/1000. See link below to Newport.
>>> 
>>> Could the error be related to that you are not reflecting directly off
>> the grating surface? The experiment shows sending the beam thru the
>> grating? If so, could there be an angle error induced?
>>> 
>>> Could it be that the grating is facing the wrong way? Thus creating an
>> offset due to the medium thickness of the grating material?
>>> 
>>> Good summary on defraction gratings.
>>> https://www.newport.com/t/grating-physics
>>> 
>>> Jim
>>> 
>>> 
>>> Sent from my iPad
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> 
> 
> 
> -- 
> 
> Chuck Hast  -- KP4DJT --
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