PURPOSE: To demonstrate single slit diffraction and multiple slit
interference.
DESCRIPTION: A slide containing a slit is positioned in the path of a
laser beam using a slide holder on a
carriage mount. The diffraction and interfernce image is cast onto a ground glass screen
and a video camera projects the image to the class. The slits have width a and
separation d as follows:
Slit Width: 0.06mm
Slit Separation: 0.25mm.
The gratings are 150 slits of .06mm width and .25mm separation, 150 slits of .03mm width 1.25mm separation, and 300 slits of .03mm width and .12mm separation.
Slides with a single slit, 2 slits, 3 slits, 4 slits and 5 slits are available. The slits are from Fisher, CFS42539 slide set and gratings.
Besides seeing a neat red light that could potentially burn your eyes (which means you should NOT, and I repeat, NOT, look at the laser directly unless you would like to become severely vision impaired.....probably conveniently before a physics exam, but even then it's not worth it), notice what is the result of passing the laser through the slits. You see some sort of interference pattern.
First, let's look at single slit diffraction. Slits that are wider than the wavelength of the beam passing through them will show diffraction patterns around the edges. As the slit becomes smaller and smaller, the light diffracts more.
EQUIPMENT: Laser on optical rail, slit slide in holder, glass screen, video camera.
SETUP TIME: 1/2 hour.
WEB RESOURCES: Single Slit Diffraction Tutorial
Updated by Jun Qi in 3/22/2000