From a previous lab, students learned that light travels in a straight line, and can travel through some substances while others block it entirely. During our next lab, we explored the question, What happens when light strikes an object?
Each lab group used a piece of white construction paper, a flashlight, two colored markers, and a self-selected object. Following the procedures, they taped the construction paper to a flat surface, we turned out the lights, and they had to shine the light on the paper and make observations. Then, we launched Trial 1, where students placed an object in the light beam near the paper and observed what happened. They noticed that a shadow of the object formed on the paper. Next, they had to draw an outline of the shadow. Students realized that the flashlight holder and the object holder had to remain very still for the drawer to complete his/her task. They labeled this shadow, Trial 1.
In Trial 2, the procedures were repeated, but this time students had to put the object in the path of light near the flashlight, the source of the light. The shadow became much larger than the Trial 1 shadow. In Closing, we explored why this occurred. With a little discussion, we concluded that in Trial 2 the object blocked more of the light because it was closer to the light source, therefore the shadow was larger. Light travels from its source outward in all directions and casts the shadow when the light is blocked. A shadow is a dark area created when an object blocks a light path. We see this all the time like when a tree casts a shadow, because it is blocking the light from the sun. We stand in the shadow to avoid the direct source of light and in turn stay cooler.
We followed the lab by reading the page from our textbooks on shadows. We learned that shadows look different outside depending on how high the sun appears in the sky, and the direction of the shadow varies according to the time of day. When the sun is in the eastern sky, the shadow that is cast is in a westward direction and is longer. At noon, when the sun is high in the sky, the shadow is shorter. When the sun is in the western sky, later in the day, the shadow is cast in an eastern direction. That makes sense to us as young scientists, because light travels in a straight line.