| Light Up My Life: Page 3 |
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- 3. Move the sensor away from the flame in at least five equal steps of distance until the illuminance reduces to about 1/100th of the original value.
 a) Measure and record the distance and illuminance at each position of the sensor.
- 4. Use the data to plot a graph of illuminance versus distance from the candle flame, as shown on the previous page.
- a) Plot distance on the x-axis and illuminance on the y-axis. You may plot the graph on a graphing calculator if one is available. Place a copy of the graph in your log.
- b) In your log explain what the graph means. (How does illuminance change with distance?)
- 5. Use a similar procedure to measure the illuminance at increasing distances from an electric lamp.
- a) Measure and record the illuminance at increasing distances.
- b) Plot a graph of the data in your log.
- c) Explain what the graph means. Is it similar or different from the relationship that you obtained for the candle?
- 6. Exploring mathematical relationships may help you find out how illuminance varies with distance.
- a) Calculate the missing values of y in the tables shown below. Record them in your log. Round off your answers to the nearest 0.01. Use the completed examples to help you get started.
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