Category Archives: Diffraction

Laser Tree Diffraction

Demo: OP-C-TD
Pira Index: 6C 10.10

 Lab Equipment  Directions
  1.  Spectra Physics laser – red
  2. Elec-Opt. laser and power supply – green
  3. Elec-Opt. laser and power supply – yellow (match laser color and # on both 2 and 3)
  4. two lab stands
  5. five 90 clamps
  6. two 3 finger clamps
  7. three adjustable lens holders
  8. lab jack
  9. three diffraction gratings
  10. plug strip
  1.  Set up as shown. Clamp the gratings in the orientation shown.
  2. Turn on lasers and set beams parallel so that three diffraction patterns are seen lined up on a wall/screen.
  3. Compare the patterns formed as each color of light is diffracted.


Poisson’s (Arago’s) Spot

Demo: OP-C-PS
Pira Index: 6C 20.10

 Lab Equipment  Directions
  1.  Spectra Physics 248 high-powered laser and power supply strapped to white board with magnet strip
  2. black plastic lab jack
  3. special can with magnets and ball bearings
  4. 18 mm lens and steel lens holder
  5. lab jack
  1.  Set up as shown with the laser supported by one lab jack and the lens and magnetic holder in front of the laser.
  2. Turn on the laser and the lens spreads the beam. Aim it at the wall.
  3. Position the can on the second lab jack so that the ball bearing on the nail inside the can is in the center of the beam.
  4. Notice the small spot of light in the center of the bearing’s shadow on the wall.


Laser Diffraction

Demo: OP-C-LD
Pira Index: 6C 10.10

 Lab Equipment  Directions
  1.  Spectra Physics 248 high-powered laser and power supply strapped to white board with magnet strip and lab jack
  2. 2 magnetic carriages
  3. single and double-slit slides (optics kit)
  4. wire and hair taped to magnetic carriage
  5. magnetic base adjustable single slit
  6. paper screen
place optics kit on the cart so that slides can be put back into the proper slits in the same box they were taken from
  1.  Set the laser and support in front of the elevated screen as shown.
  2. Put the single slit slide on the magnetic carriage. Adjust the slide position to allow laser to shine through the slit and onto the screen. When alignment is complete to show the pattern well or the screen, remove the screen so that the pattern can be seen on a wall.
  3. Substitute the double slit for comparison. The adjustable slit can also be shown.
  4. Substitute the wire and hair carriage to show the diffraction pattern around the hair strand or wire.

Fresnel Zones

Demo: OP-C-FZ
Pira Index: 6C 20.40

 Lab Equipment  Directions
  1.  Pasco optics bench (long)
  2. Laser
  3. Pasco photometer
  4. Pasco linear translator drive
  5. Fiber optics cable
  6. Slides from Pasco optics kit: A) Light source aperture #9118 B) Variable diaphragm #9117 C) 48 mm convex lens #9133 D) 18 mm convex lens #9132
  1.  Set up as shown. Line #9118 up so that the beam goes through on of the apertures. Adjust the top knob on #4 and the sensitivity knob on #3 until you get about a half-scale deflection on #3.
  2. Slowly close the diaphragm watching the intensity scale of the photometer. With proper adjustment of positions of the components you should see the intensity gradually decrease as you close the diaphragm. But watch carefully – a one point needle will rise, indicating an intensity increase.
Caution: Don’t bend the fiber optics cable – it is sensitive to flexing.


Diffraction Bench, Pasco

Demo: OP-C-DB
Pira Index: 6C 10.00

 Lab Equipment  Directions
  1.  Pasco optics bench (special track)
  2. Pasco rotating slit disks and screen
  3. Electro-Optics laser and power supply
  4. lab pole
  5. telescope clamp and block
  6. 2 c-clamps
  7. 90 degree clamps
  8. 3 finger clamp
  1.  Set up laser assembly as shown.
  2. Place the single-slit disk facing the laser and only a few centimeters from it. Level the laser to properly align with the selected slit. Use the C-clamps to hold the bench in position.
  3. Turn the disk to align various slits with the laser beam. A paper can be placed on the screen so that patterns can be reproduced and measured.
  4. Remove the single-slit disk and mount the multiple-slit disk in its place.