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Refraction is one of those things that everybody knows about, but nobody really knows how it works.  For instance, everybody has seen how a straight object like a straw or a pencil can look "bent" when part of it is out of a liquid and part of it is in a liquid.  How does this happen though? 


*This is just the basic principle which I've adapted from Richard Feynmans "QED - The Strange Theory of Light and Matter"

The basic principle behind refraction is that light moves slower in water than it does in air, and light will always take the quickest path to get from A to B.

Think of a lifeguard running to save someone 50 yards up the beach and 50 yds in the water, they can run faster on land than in the water, so it doesn't make sense to run straight at the person because they will spend a long time in the water, which is slow.

It also doesn't make sense for the lifeguard to run to the point on the beach where they can swim straight out - that's just too much distance to cover. Instead, there is an angle that they can take to the water before heading straight to the swimmer that will take the least amount of time.

This angle tells you how much the light will "bend" when moving from water to air.

lifeguard and swimmer angle of refraction

Did I miss something?  Let me know


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