Measure the wavelength of laser light

Your job is to use the double-slit interference pattern to determine the wavelength of light emitted by a laser.

Set up an optics bench, laser, and Multiple Slits wheel as shown. Place a piece of paper on the wall, so that the distance L is more than one meter (the larger, the better).

You should be able to find positions on the wheel which have two slits separated by
1. d = 0.50 mm
2. d = 0.25 mm
3. d = 0.125 mm
For each position,
1. shine the laser through the slits and onto the paper. Mark the location of a number of spots near the center -- I recommend the spots number 2, 5, 8 from the center on each side. If you can't see these particular spots, pick others which are nearby.
2. Take the paper off the wall. For each of the three index numbers (m = 2 and m = 5 and m = 8 in my example), measure the distance from the center of the pattern to the m'th spot. See example below.
In the example above, Joe is measuring the distance between the m = 4 spot to either side of the center. It's a good idea to measure the FULL separation, from the left-hand m = 4 spot to the right-hand m = 4 spot, and then divide by two.

Make a table of your measurements. Your table should have nine rows: three measurements for d = 0.50 mm, three measurements for d = 0.25 mm, three measurements for d = 0.125 mm. Be sure to include the separation of the slits, the width of the slits, the index of the spots you measured, and the distance y of each spot from the center. Don't forget the units!
Now, compute the wavelength of the light. Make a graph which uses all your measurements to find the wavelength (and uncertainty). Use the equation
```
                                (  L * m   )
               y   =  lambda *  ( -------- )
                                (    d     )
```
and choose quantities for your axes so that the slope of the line on the graph is the wavelength lambda.

Does your wavelength make sense? What is the range of wavelengths humans can see? What color is the laser?