Equipment List:
Pasco wave optic kit with lasers.
Two meter sticks
Masking tape
Procedure:
Find the single slit diffraction slide in your kit;
it will have four slits each of a different given width. Find the circular
aperture slide in you kit; it will have two circular apertures with their
diameters given. Put the laser on the optical bench (the extra, smaller
optical bench is not neccessary). Using the masking tape, tape a
piece of white paper on the wall away from the laser such that the laser
beam will shine onto the white paper.
Make sure you do not look into the laser or move the laser so that the light goes into someone else's eye.
Put the slide of rectangular slits on a lens holder and place the holder on the optical bench close to and in front of the laser. Gently position the slide so that the laser light goes through one and only one slit (this may require patience). You should record which slit the light is going through and then on the white sheet of paper (your "screen"), record the distance from the centers of the minima on each side of the central maximum. That value divided in half is your "y" value. Repeat this procedure for each of the four slits.
Take off the rectangular slide and put the other slide with the circular apertures on the holder. Now construct a screen that will fit onto the optical bench (maybe the white sheet attached to a lens holder). The screen should be close to the aperture or you will not be able to see the the circular diffraction pattern and its central maximum. Measure the diameter of the central maximum by measuring from the center of the first minima ring around the central maximum to the center of the same minima ring on the other side of the maximum. Repeat for the other aperture.
Calculations:
Using the datat for the six different apertures, calculate the wavelenght of the laser light with an uncertainty. Compare to the known value of the wavelength.
Relevant links:
Diffraction
applet