Refraction - medium, index of refraction, prism, transparent
Refraction
medium, index of refraction, prism, transparent
Light Unit
Light is a speedaholic. It loves speed! It wants to move as fast as it can through anything that
gets in its way so it can continue to shoot through the universe. Light normally moves in straight
lines. But when it reaches something new, like a piece of glass or water, it will change direction to
find the fastest way through. Just like you might change directions when you run from an empty
field into a crowd. When light exits, it will bend because it's free to move how it wants to. This is
called refraction.
Have you ever tried to run against the wind? It's hard, right? It pushes against you. But if you run at an
angle you can keep moving fast. How about running through water? Even harder, right? The water grabs
your feet and holds your body back. Like you, there are some things that light can pass through more
easily than others. Light will move more quickly or slowly, straight or at an angle depending on its
medium. And no, that's not the shirt size between large and small. Medium is another word for the
substance that something moves through. Light and glass, air and water -- these are different mediums
that light uses to move. Refraction happens when light moves from one of these to another, say from
water to air. It's this change that makes light bend.
You can run through a screen door much more easily than a wooden door. This isn't a science
experiment. Please don't try it. Like you, the easiest things for light to move through are the ones that are
clear or transparent. When something is transparent, it means you can see through it. Have you ever
shined a light through a glass of water and then tried shining one through a glass of milk? The light shines
clear and bright through the water glass. Can you see the light bend? Try filling a clear glass with water
and then sticking a pencil in at an angle. The light from the pencil will bend and it will look like it's made of
rubber.
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Refraction - medium, index of refraction, prism, transparent
So what is it like to be a bending beam of light? Have you ever pushed your way through a crowded place
to get to an exit? You have to step and weave around people. You'll probably need to go in a different
direction than a straight line in order to get where you're going. Once you reach the exit, you are free to
move quickly and in any direction. Like you, light wants to find the fastest way through! In water, light has
to move at an angle to get through. When it reaches the air, it will move in a more straight path. Science
uses a number called the index of refraction to measure how much light speeds up or slows down when
entering a new space. It measures that moment when you burst out of the exit and are free to move
quickly.
Some things can only bend so much before they break, and light is no different. But when light breaks,
something beautiful happens. The best way to break light is with a prism. A prism is a glass triangle with
long, rectangle sides that can split white light into different colors. Because of the way it's shaped, it will
bend light and then immediately bend it again, making it break up into smaller parts, showing you a
complete rainbow! White light has all the colors inside it ""• red, orange, yellow, green, blue, indigo, and
violet. Each color bends just a little more than the last. Red bends the least and violet the most. So,
when light enters a prism and is bent and then bent again, the colors separate like a rainbow fan. But by
holding a second prism up to the rainbow, you can put the colors back together into a single beam of white
light.
Picture a race with your friends. You move through a windy field, through a pool, across an open lawn,
and then through a crowded building. In order to find the way through, you have to move in all different
directions, sometimes slowly, sometimes quickly. That's what it's like for light to move through our world . .
. just millions of times faster.
References:
Hyperphysics. "Refraction of Light"• GSU, 2000.
<http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html>
How Stuff Works. "How Vision Works""•Refraction"• How Stuff Works, 2009.
< http://science.howstuffworks.com/environmental/life/human-biology/eye6.htm>
eHow. "How Prisms Work"• eHow, 2010.
< http://www.ehow.com/how-does_4965588_prisms-work.html>
Over 300 more free Science and History articles are waiting to inspire your students at BirdBrainScience.com
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Refraction - medium, index of refraction, prism, transparent
How Stuff Works. "What Causes a Rainbow"• How Stuff Works, 2011.
< http://science.howstuffworks.com/nature/climate-weather/atmospheric/question41.htm>
Over 300 more free Science and History articles are waiting to inspire your students at BirdBrainScience.com
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