[Laser] Chucks question continued

[Jim Moss]

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
> ______________________________________________________________
> Laser mailing list
> Home: http://mailman.qth.net/mailman/listinfo/laser
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Laser at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html