Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum

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Teacher's Lab
The Science of Light
IntroductionLight in ColorLaws of Light

how this works
across the grades

how this works

colors imageIf you are like the author, you tend to move the player in the wrong direction every time you try to put the player in the right spot. The shadows just seem to go the wrong way. The whole situation seems simple, but it can be more subtle than you might think.

So think about why the shadows are there. A shadow is not a thing in itself, but rather the absence of light. In this activity, the "bright grass" is illuminated by four lights. In a shadow, it is illuminated by only three; one is blocked by the player.

You can see multiple shadows whenever you have multiple light sources. If you have more than one light in a room, your hand will cast more than one shadow. If you have a chandelier with only a few bulbs, each bulb will cast a separate shadow, giving you a bouquet of shadows in the same shape as the chandelier. (If there are lots of bulbs, or large light sources such as fluorescent bars, the shadows get washed out.)

But why are short shadows darker? On the sports field here, if the light is nearby, the angle will be higher and the shadow will be shorter. Now here's the tricky part: the nearby light, being closer, provides more of the illumination. The other three lights are weaker, being farther away, so the field in shadow is darker than if the player were in the middle of the field.

You can see this effect in everyday (or every-night) life if you live where there are streetlights. Go for a walk down the street at night. As you proceed from light to light, you will see two shadows: one from the light behind you and one from the light before you. As you approach a light, the shadow behind you will darken and shorten, while the one in front of you gets more and more faint.

There are two phenomena here: the fact of multiple shadows and the effect of distance on their darkness. The first is easy for young children to understand; as they get older, they can come to understand the second.

Back to Where Is the Player?


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