The Earth, Sun and Moon 37 Activity Angle of sunlight
In this investigation you will use a torch and a piece of paper to model the amount of solar energy reaching the earth’s surface.
Apparatus Torch Sheet of graph paper Ruler Protractor
Method Angle of torch
90o 75o 60o 45o 30o 15o
1. Set up as shown in Fig. 14 above. The torch may be held in place using a retort stand. Estimate the area of the graph paper illuminated by the torch beam. 2. Use a ruler and protractor to vary the angle at which the torch beam hits the paper. Keep the torch at the same distance away from the paper as you vary the angle.
3. Record your results in the table. 4. Use your data to plot a line graph of the illuminated area against the angle of the beam.
Questions What angle caused the beam to cover the largest area? Why is it important to keep the torch at the same distance from the paper as you vary the angle? Describe how this model can explain the relationship between the angle of the sun and the amount of energy that reaches Earth’s surface.
