Procedure:

Single slit experiment:

The single slit diffraction pattern should have minima at

(_min) = n (a) for n = 1,2,... where $a$ is the slit width, and $\lambda$ is the given wavelength of the laser light.

1. Observe the single slit diffraction pattern, and make the necessary measurements to determine the angles associated with minima. Be very careful to make the distance to the optical backdrop long enough to make measurements of the minima and maxima easy to do.
2. Use the traveling microscope to measure the width of the slits, and thus experimentally determine the wavelength of the light.

Double slit experiment: If light is a wave, an interference pattern should be created, and if we are lucky, it will even be visible, much like that observed in the single slit experiment with this difference: there are minima within the maxima.

The maximum should appear at angles $\theta_{max}$ where d (_max) = m for m = 0,1,2,... and the minima should appear at d (_min) = ( m + 12 ) for m = 0,1,2,... where $d$ is the distance between the slits.

1. Observe the double slit interference pattern, and make the necessary measurements and thus determine angles associated with the maxima and minima.
2. Use the traveling microscope to measure the distance between the slits and thus determine the wavelength of the light.

Multiple slit experiment: A diffraction grating consists of a regular array of slits or bars with equal spacing. The condition for maxima is the same as for a double slit. Observe the pattern produced by the diffraction grating and record the measurements necessary for calculating the angle of the first diffraction maximum. From the number of lines per inch, deduce the wavelength of the laser light.