Unit 10: Light Properties (refraction)

Today was all about refraction. Refraction id the bending in waves due to change in media. For example, when light shines through a pool, the light doesn't shine in a straight beam, it looks like its bent. This is refraction because it bends form the change in the material the light is in. One major rule for refraction is that when moving from a fast medium to a slower medium, light will bend toward the normal. The normal is the force perpendicular to the surface.

In the picture above, the laser is moving through a fast medium at first, then the medium changes to a slower medium, causing the laser to bend. Then the laser moves back into a the faster medium again and is going at the same velocity and angle as it was before. As you can see, the laser wanted to continue going in the same direction after hitting the different medium, represented by the dotted green line, but the laser bends in the slower medium toward the normal (N) force, which is represented by the dashed blue line.

Different colors bend at different rates. Red bends less and blue bends more.

Another important rule to remember is Snell's Law which is: n1sinθ1 = n2sinθ2. "n" is the index of refraction, which is a ratio, so there are no fractions. n = c/v. "c" is the speed of light in a vacuum, and "v" is the speed of light in the medium. Here are some common ones:

nvacuum = 1

nair ≈ 1

nH2O = 1.33

nglass = 1.5

ndiamond = 2.42

All angles are relative to the normal. When the light is moving from a fast medium to slow medium, the light bends toward the normal, whereas when the light moves from a slow medium to a fast medium then the light bends away from the normal.

We also learned about lenses. Lenses can be either concave or convex. When light goes through either of them, the image created can either be real or virtual, inverted or right-side up, and reduced or enlarged.

In the picture above, I am holding up paper and a magnifying glass because in class we used convex lenses to create a focal point with the sun's light and burn paper. That is why the paper I am holding up has holes in it.

hehehe.