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How Light Travels:
Comparing Light Sources:
Background For Teachers:
Light travels so fast that it seems we see things the instant they happen. Light travels at 300,000 km per second, or 186,000 miles per second. Light travels in straight lines. When light hits an object, it can be absorbed, reflected, or pass through (transmitted). If light passes through a transparent object at an angle, it can also be refracted, or bent, because the speed of light slows as it passes from one transparent object to another.
All objects reflect some light, because we can see them, but objects that are smooth and hard are better at reflecting light than others. Mirrors are excellent reflectors because the surface is smooth, and light is able to bounce back. When light hits a surface, it is always reflected at the same angle it strikes the surface. The law of reflection states that the angle of incidence equals the angle of reflection. This is best demonstrated by throwing a ball at a smooth surface. The angle at which it hits will equal the angle at which it bounces back (45° going in equals 45° going out).
With a transparent object (air, water, clear glass) almost all light passes through. Translucent materials (wax paper, bathroom windows) allow some light to pass through while some light is reflected. Opaque materials (wood, metal) block all light and either reflect or absorb the light. As light passes from one transparent material to another at an angle (from air to water, or air to glass), the light will slow down and appear bent. This is called refraction. A good example of this is placing a pencil in a clear glass of water. The part of the pencil above the water appears to be broken off from the part below the water. Light shining through a glass or Pyrex® baking pan filled with water demonstrates refraction.
Intended Learning Outcomes:
Invitation to Learn
If you have adequate materials and books for the whole class to do the experiments at the same time, it will be easier to explain the procedure to everyone, and then you can have a discussion at the end of each experiment to ensure that students learned what was expected in the experiment.
Prepared worksheets that teachers can run off for the light
centers are included with this activity. However, greater
learning takes place when students are able to design and
construct their own lab sheets instead of continually using
prepared ones. The best way to facilitate this process is to
have prepared worksheets for the teacher to model and
As we do the labs together at the CORE Academy, we begin with completely outlined lab sheets, then learn how to create our own lab sheets, and finally blank paper will be distributed for the last light labs.
Center Set up
If this is a first time students are working at centers, stop everyone at the end of the first center and have each group share one thing they did well as a group, and one way they could improve. Repeat one or more times as needed.
Use the lab sheets to assess what students do and do not understand.
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