1. Turn the light on as bright as it will go, then back down until the "H" on the knob is lined up with the black mark on the base.
2. Make sure the 9-V batteries are pushed into the light detector, and the alligator clips are attached to the circuit wires (the green wire should be next to the green mark on the base).
3. Place the detector (facing the light) at a distance of 30 cm from the light (measure from the edges of the wooden boxes). Using the dial to adjust the light's luminosity until the current reading is 20 milli-Amperes (mA, that's 1/1000th of an Ampere, a unit of electric current).
4. Now change the distance of the detector from the light until you get the different electric current values in the table below. For each current value, record the distance you measured.
   

   Data Collection Table

   
   
5. Plot the data points you have collected on some graph paper.
   

   Graph paper with labels

   
   
6. On the same plot, plot the "inverse square law": I is the current (or brightness), d is the distance, and A is just a constant number. If you adjusted the light properly so that I=20 mA when d=30 cm, can you figure out what the constant is? You will need this to make your plot.