A Cause for Reflection
In December 2012 the Explorers learned that one of the best experiences you can have is when you not only understand an interesting scientific concept, but you also discover a way to USE that concept in a cool way.
The group continued its recent focus on vision and sight by investigating a central property of light itself. Except under extreme gravitational conditions (such as near a star or, even better, a black hole), lights travels only in a straight line. It doesn’t curve, it doesn’t weave, it doesn’t zigzag. However, it CAN bounce.
When light (or any other type of wave) strikes an object, it bounces off in a new direction. This bouncing is known as reflection, and one of the properties of light waves says that when they strike a flat surface, the “angle of incidence equals the angle of reflection.” That’s a fancy way of saying a simple thing: whatever angle the light waves hit the surface at, they will bounce off the surface at the exact same angle. If you stand directly in front of a mirror, you are at a 90 degree angle to the mirror, and the light waves from you will bounce straight back at that same 90 degree angle—which allows you to see your image reflected. If you move to the side so that you are at an angle to the mirror, you won’t see your own image in it—instead, you’ll see the image of whatever lies to the other side of the mirror AT THE SAME ANGLE as your own to the mirror.
This concept takes a little visualization to comprehend, and the Explorers spent a few minutes testing it out with a small mirror and a laser pointer. As Mr. Ramsey moved to different spots while pointing the laser at the mirror, the reflected laser dot also moved to different locations, and an imaginary line drawn from the laser pointer to the mirror always made the same angle as another imaginary line from the mirror to the reflected dot. (See the first picture in the photo gallery for a diagram of how this actually works!)
Interesting, perhaps, but how can that idea be applied to something practical? Captains of submarines found a way years ago to put this knowledge to use. When a submarine is under the water, knowing what is happening above would be very helpful (any enemy ships lurking around?), but there is no direct way to see what is happening on the ocean’s surface. However, by using a pair of mirrors in a device known as a “periscope,” the light from the surface can be bounced down to the submarine and then bounced again into the eyes of the captain. In essence, a periscope lets you fold the light’s path in a way that makes it possible to see around corners.
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Using poster board and a pattern, the Explorers each cut out and assembled a rectangular box with openings at both ends. The key, though, is that the openings face in opposite directions, and each opening has a surface angled at 45 degrees. After they finished completing their periscope box, each Explorer had a pair of mirrors taped onto these surfaces by Mr. Ramsey. Now the light could enter the top of the periscope, be bounced by the first mirror down the box, and then be bounced by the second mirror out the bottom opening into the student’s eyes. Presto—an instant spying contraption! (Again, see the second picture in the gallery for a diagram of how a periscope works.)
To see some photos of our periscope activity, check out the gallery (thanks to Lissa McMeans for taking the pictures!). Click on the links below for more information about periscopes.