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# Science_Lab_Yellow / Lesson 7: Light Rays Bend?

 Light Passes Through What will we be learning today? In this lesson, we are going to learn all about what can light pass through.

How Can Light Rays Be Bent?

The pencil in the photograph certainly appears to be bent. However, the bend is actually just a "trick" that light rays play on our eyes. The illusion is caused when light rays from the lower part of the pencil change direction as they go from water into air. The bending of light rays as they pass from one substance into another is called refraction(ri ·FRAK ·shuhn). The second photograph illustrates the refraction of a light beam.

 Light rays bend as they go from water into air, making the pencil appear to be bent.

 How does light affect what you see when it passes through water? You've seen that light rays may bend as they move from one substance into another. Can light rays move from one substance into another without bending?

 How Refraction Works Imagine skating onto grass from a sidewalk. If you skate straight onto the grass at a 90 ° angle, you will slow down, but your direction will remain the same. If you skate onto the grass at any other angle, though, one skate will slow before the other. This will cause you to turn in a new direction. The shallower the angle between your original path and the grass, the more your direction will change.

 Like a skater, light traveling from one substance into a denser substance slows down. (The denser substance is made of material that is packed together more tightly than the material that makes up the less-dense substance.)

 If light strikes the new material head-on, its direction is unchanged. However, if it strikes at any other angle, it gets refracted into a new direction. The amount of refraction increases as the incoming angle gets shallower.

 Look at the photos of the skaters. The first skater skates onto the grass at a 90 ° angle. Both skates hit the grass at the same time. The second skater's skates don't hit the grass at the same time. Why not? How will the path the second skater takes differ from the path the first skater takes? How do the paths the skaters take compare with the paths the light beams take?

 Let's Review What We Learned Today! Now complete your PDA!