Light Intensity Experiment

Question:

What is the effect of distance on the intensity (brightness) of light?

Background:

Light gets brighter the closer you get to the light source. A beam of light gets wider the farther away from the source, except a laser.

Hypothesis:

If a light is twice as far away then the brightness will be one half as much because experience shows that the light gets dimmer with distance.

Materials:

• Overhead projector for a bright light source
• Solar cell for the brightness sensor
• Milliammeter (current meter) to measure the solar cell current
• Meter stick

Procedure:

1. Place the overhead projector in front of a wall..
2. Turn the projector so the light shines on the wall.
3. Place the projector so that the lens is 0.5 meters from the wall.
4. Tape the solar cell to the wall so that the cell is centered in the projector light beam.
5. Connect the test lead of the milliammeter to the solar cell. Red test lead to the red wire of the solar cell.
6. With only one

Data:

 Distance from wall(m) Light Current (mA) 0.5 3.84 1 1.02 1.5 0.48 2 0.28 2.5 0.20 3 0.14

Conclusion:

The hypothesis is "

If a light is twice as far away then the brightness will be one half as much because experience shows that the light gets dimmer with distance." The hypothesis was not correct. When the distance was doubled the brightness went down by more than 1/2.