Goal: to measure the wavelength of the red and green He-Ne lasers using a standard CD
            as a reflection grating.

Before Lab: familiarize yourself with the condition for constructive interference for a
                     transmission grating by reading Cutnell and Johnson section 27-8 (on The
                     Diffraction Grating).
                     If you don't do this, you won't know what to measure tomorrow.  The conditions
                     for constructive interference for transmission and reflection gratings are the
                     same.

Experimental set-up:
 

                   CD        <---- laser light                                                 wall
 

    the laser light will have to be angled up slightly so that the reflection goes over the top of the
    laser rather than reflects straight back at the laser (and is thus blocked from hitting the
    wall).  Try to minimize this angle, however.

    other experimental suggestions:

        tape the laser to the table so it is stable
        use a ring-stand with clamp  to hold the CD
        (the equipment should be available in Lab 1)
        make sure that you measure positions of the 0th order CI and both 1st order CIs
            on the plane of the wall; these are necessary to determine the reflection interference
            angles q ; I doubt that you will be able to see second order CIs; what other distance
            measurement do you need to make to determine q  ?
        use a tape measure to accurately measure distances
        be as accurate as possible in all of your meausrements

        all data should go directly in the lab book according to usual lab practices (in ink, etc.)
        if you are prepared, you should have enough time to perform accurate measurements
            AND finish the calculations, write-up, and summary/conclusion

        The separation of adjacent CD grooves is 1.6 mm
 

Due date:  Tuesday, March 23