# Single Slit Interference and Diffraction Gratings

The web lesson for this is pretty light and consists mostly of links to other websites. There are some important things to note about both diffraction gratings and single slits. Diffraction gratings may be treated exactly the same as a double slit problem. In other words,

What makes the diffraction grating unique is that you get very defined maxima and minima due to the effect of multiple slits that are very close together. To figure the distance, d, between the slits, simply take the inverse of the diffraction lines in meters. For example, if a grating has 10,000 scratches per .01 m, then the distance between slits is .01m/10,000 = 1 x 10-6 meters.

For more on diffraction gratings, try:

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/grating.html#c1

http://physics.bu.edu/py106/notes/Diffraction.html

Single Slit problems, on the other hand, are a bit different. Light is bending around a single slit and the wavelets essentially interfere with themselves. As such, you get a very pronounced central maxima that is twice as wide as the other maxima in a single slit. The formula for finding the location of the maxima for single slits is:

where m is the order of magnitude, D is the width of the slit in meters, and q is the angle between the center of the central maxima and the first minima. By the way, in single slits, minima occur at the integer multiples of the wavelength. This is exactly the opposite of what happens with double slits.

For more on single slit diffraction and disc diffraction, try:

http://online.cctt.org/physicslab/content/PhyAPB/lessonnotes/twosourceinterference/slitpatterns.asp

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/cirapp2.html

The NTNU Virtual Physics Laboratory provides several excellent applets that demonstrate principles of Physics. Click Here for an applet you can run from the NTNU Virtual Physics Laboratory that will show single and double slit interference.

For Practice Problems, Try: Giancoli Multiple Choice PracticeQuestions (Questions 1-12)