Getting to Know the Light Probe

This experiment is designed to learn something about light and the light probe. Begin by connecting a TI-82 to the TI-CBL using the linking cable and the linking ports at the bottom of the two units. There is only one port at the bottom of the TI-82 but there are two ports at the bottom of the TI-CBL. The linking port is the smaller of the two. Next connect the light probe to the CH1 port on the top of the TI-CBL. Now turn both units on. Press the PRGM key on the TI-82. You should see the program menu as shown on the leftmost screen below. Use the down arrow key to arrow down to the program ALIGHTRT as shown in the second screen below. Press the ENTER key on the TI-82. You should see the third screen below. Press the ENTER key once again and you should see the last screen below.

Now look at your TI-CBL. The READY indicator should be on and you should see a light reading. As you point the light probe in different directions, the reading should change. The readings are in units of mW/cm^2. Now you can disconnect the TI-CBL from the TI-82 and use the TI-CBL with the light probe still attached to explore light and the light probe.

• Does the light probe have to be aimed directly at a light source to measure its intensity?

• Hold the light probe carefully in a fixed position at a fixed distance from an incandescent light source. Repeat this experiment with a fluorescent light source or with a television or computer monitor. Do you notice anything unexpected?

Now go on to the next experiment -- Fluorescent Lights and Television Screens -- A Story with a Moral.