SAMPLE ANSWERS: Seasons Lab - Questions and Conclusions: 1. The independent variable in the Reason for the Seasons lab was the angle of the light. By tilting the book away from the flashlight, we changed the angle of the light shining onto the graph paper. 2. The dependent variable in this lab was the size of the area on the graph paper that the light shone. We measured the size of this area by counting the number of squares that were in the light. 3. In this lab, we were demonstrating how the angle of light affects the amount and intensity of light shining on a surface. Since the angle of the light was our independent variable, this is the only thing we could change and all other factors that might affect our results had to be kept constant. An example of a constant in this experiment is the distance between the flashlight and the graph paper. We had to hold the graph paper at the same distance every time we changed the angle because changing the distance could have affected how much light shone on the graph paper. Whenever you change more than one variable, you do not know which one caused your results. 4. In addition to the starting distance, some other constants in this experiment were the height of the stack of books, the amount of light shining from the flashlight, and the size of squares on the graph paper. It was important to keep these factors constant because changing them could have affected the amount of light shining on the paper. For example, if we had used a larger flashlight for some trials, we would not be able to say if the larger area of light on the paper was due to the angle or to the flashlight itself. 5. As the degree of tilt increased, so did the number of squares inside the outline. The light from the flashlight was more spread out when the angle was greater. For example, when the book was straight up and down, 75 squares were lit up. As we tilted the graph paper farther and farther. More and more squares were contained within the lit up area. By the time we reached the largest angle, 40°, there were 300 squares within the lighted outline. (note: I made up this data; students should cite their actual data.) 6. As the degree of tilt increased, the light became dimmer, or less intense. The same amount of light was being spread out over a larger area, therefore each individual point within the outline received less light than it had when the angle of the graph paper away from the light source was smaller. 7. This experiment models the way that the angle of sunlight reaching the earth determines the season. Earth’s seasons are caused by the varying amount and intensity of sunlight at different times of year. The greater the angle, the less concentrated, or intense, is the light shining on the surface. The light spreads out more, but at any given point it is dimmer. During our summer, the northern hemisphere is tilted toward the sun and therefore receives more direct, concentrated sunlight. During our winter, the northern hemisphere is tilted away from the sun, so the light is spread out and less intense. 8. When the book is held vertically, or at 0 degrees of tilt, we see light similar to what North America experiences in summer. It is concentrated into a smaller area and therefore more intense. If we want to model the actual tilt of the planet toward the sun, we’d have to angle the book toward the flashlight, but we did not do that. 9. When the book is tilted 20 degrees away from the light source, it produces light similar to what North America experiences in winter. This is because the earth is tilted 23.5 degrees on its axis and 20 degrees is the closest angle we used. 10. As stated earlier (question #7), the experiment helps us to see how the angle of light affects its concentration. Our data indicates a direct relationship between the angle of the light shining onto a surface and the concentration of the light that hits that surface. As the angle away from the light source increased, the concentration of light hitting the surface decreased. Every time we increased the angle of tilt, the area lit up increased, which caused the light to be more spread out and less concentrated.