PROCEDURE:

1. Position the light source at the left end of the optical bench.
2. Attach the diffuser, double-slits and photometer apertures to three separate component carriers.
3. Position the double-slits about 20 cm from the light source. Place the photometer apertures between the light source and double slits.
4. Pick a sufficiently large single slit on the photometer aperture slide and adjust the position of this slit until one set of double slits is fully illuminated.
5. Position the diffuser behind the double slits and adjust its distance from the slits until there is a sharp geometrical image of the two slits. (View the image from the side of the diffuser which faces away from the light source.)
6. Move the diffuser slowly away from the slits until the sharp geometrical image becomes an interference pattern with several maxima and minima.
7. Adjust the single slit (i.e. one of the photometer apertures) until only one of the double slits is illuminated. Observe the image (it is not a clear image, but rather a diffraction pattern).
8. Now illuminate both slits and observe the image. Notice that some points previously illuminated are now dark.
9. Move the double slits and diffuser to the far right of the bench and observe that the single slit is no longer necessary. (However, you still need some sort of edge to cover one of the double slits in order to examine the two different patterns. It is convenient to attach the aperture mask to the same component carrier as the double slits. Adjust the mask's position to allow one or two slits to be illuminated.
10. Attach the photometer's fiber optic probe to the linear translator and use the translator to scan the images. Place a small aperture such as the light source apertures in front of the probe on the rear surface of the analyzer holder. Adjust the aperture so that light incident on it enters the probe. Using the aperture minimizes effects due to ambient light. Plot intensity versus position for both one slit uncovered and two slits uncovered.
11. Measure the intensity of the bright middle band ( ) and then measure the intensity at the middle of the first shaded bands on either side ( ). Calculate the Michelson visibility coefficient (V) from:

    

    This coefficient gives a measure of the coherence of the incident light with V=1.0 indicating perfect coherence.