This application simulates a small Michelson interferometer very much like one of our laboratory setups. The goal is to align all the mirrors on the table until you see a regular pattern of dark and light bands ("fringes") appear on the monitor in the lower left corner.

It is probably a good idea to read through all the instructions below before you start the demo. When you are done, move the lamp to a new position and repeat the process. After several rounds you will see how the delay line setting changes as you change the angle to the lamp.

Once you know the relation between the angle to the lamp and the delay line setting, you can measure the location of the lamp by reading the delay line setting. This is how astronomers use interferometers to determine the exact location of a star on the sky.

The demo requires requires a Shockwave plug-in for your browser. If you don't have this software, the link to the demo will take you to the Macromedia site for a free download.

If you are familiar with the instruction, you can go directly to demo.

Instructions and Preview

1. Move the light source along the baseline by dragging it with the cursor.

2. Click on the light switch to turn on the light on.

3. Use the control for the right mirror until you send a beam of light through the right arm of the interferometer. You might have to turn the mirror in small steps.

4.  Adjust the left mirror until you also send a light beam through the left arm of the interferometer. You might have to use small steps.

5. Change the position of the delay line using the control button until you see a fringe pattern on the monitor.

6. You might have to adjust the delay line position carefully until you find the correct position. Interferometers are sensitive!

No fringes.

Fringes found!

7. Click on the plot button to plot the delay setting you just found versus the angle to the light source.

8. Start over at step one and use a different position for the light source. You will slowly build up a plot of the relation between the angle to the source and the delay line setting.

I am ready, take me to the demo now.