6C20.20-Thin Wire Diffraction

6c2020thin wire diffraction

Description: A narrow opaque object will create a diffraction pattern that may be used to measure the width of the object.
The diffraction pattern is like that of a narrow slit, with the width of the object replacing the slit width.
You can try this with a fine wire or strand of your hair.


  • Optical bench
  • Laser on post
  • Magnetic stand and magnetic slide holder
  • Either a piece of hair or a thin strand
  • Tape
  • Tape measure

Setup Procedure:

  1. Insert the laser into the optical bench.
  2. Insert the magnetic stand into the optical bench.
  3. Ask the professor if he/she wants to use their own hair, or have you pre fit it with a small stand.
  4. If the professors wants to use their hair, include some masking tape.
  5. If they want it pre fitted, cut a small thin opaque strand and tape it onto the magnetic slide holder.
  6. Place the magnetic slide holder onto the magnetic stand and align so the laser will shin on the string.
  7. Setup in the classroom to allow for the most distance between the laser and screen.

Demonstration Procedure:

  1. If using your own hair, take a stand out and tape it onto the stand (see picture).
  2. Turn on the laser and make sure it’s lined up on the thin wire/hair.
  3. (Optional) Turn off the lights.
  4. Note the diffraction pattern on the screen is very similar to a single slit diffraction.
  5. (Optional) Take the appropiate measurments with the tape measure to calculate the width of the thin wire/hair.
  6. When finished, turn off the laser.

Caution, Laser Laser Light
Do not stare into the beam. Keep away from students eyes.