|
| |
Interference and Diffraction
The lasers you will be working with today are very low power.
However, damage to your eye could occur if you look directly into the beam. If
there are two groups at your table, be sure that you have your lasers point away from one
another. The wavelength of the laser beam is 632.8 nm.
Set-up your laser on a lab jack at the end of the optical bench.
Use the lens holder to hold your multiple slit slide. Place the slits on the
end of the optical bench near the laser. The exact distance between the slits and
the laser doesn't matter. Place your screen 1 meter from the slits. Adjust the
laser beam so that it passes through the slits by raising or lowering the lab jack.
Part I: Two slits
Observe and describe in your notebook the interference pattern of a
laser beaming passing through two slits.
Measure the locations of at least 6 interference minimums.
The easiest way to do this is to hold scrap paper against the screen and make a
very narrow mark at the location of each minimum. Then move the paper to the
tabletop and use your ruler to measure the distance of each mark from the center.
(Estimate to the nearest .5mm)
Make a quantitative sketch of intensity. Use graph paper.
The positions of the minimums should be accurate, but the intensity scale is only
relative.
Calculate the distance between the two slits for each data
point. Find the average slit spacing and percent error.
Part II: Single Slit
Part III: More than 2 slits
Observe the pattern for two slits again, then observe the patterns
for 3, 4, 5, and 6 slits.
How are the multi-slit patterns similar to the two-slit
pattern? How are they different?
Replace the slits with a diffraction grating. Change the slit
to screen distance to 10cm.
Measure the position of several diffraction maximums.
Calculate the slit spacing with percent error.
Determine the number of slits per centimeter in the grating.
Compare your calculation to the number supplied by the
manufacturer.
|