RAY DIAGRAMS and REFRACTION IN NATURE This is NOT refraction, but it’s funny… Tahoma Jr. High 8th Grade Science Maple Valley, WA

Mirrors reflect, and make the image appear as if they are behind the mirror. Because of reflection the image appears farther away. Mirrors follow the Equal Angle Rule for each light ray – the angle coming in, is the same as the angle going out.

Forget all the letters in the picture, just notice that a concave mirror makes the rays converge on one point (the “Focal Point”) – just like a satellite dish! Weak signals are concentrated into one point.

You’ve seen guys like this at football games running along the sidelines. They’re picking up faint sounds on the field and using their parabolic microphones to make them louder. This guy, however, is listening to hummingbirds! It’s a concave mirror! He’s also using lenses in the binoculars to look at the hummingbirds!

Funhouse mirrors are just that… FUN!

Sideview mirrors (convex mirror) may distort the image, but they help eliminate blindspots!

Can you name all the lenses here? A: double convex B. single convex C. convex / concave D. double concave E. single concave F. convex / concave (but more curve than “c” equals more refraction) This is how eyeglass work, the inside curve is different from the outside curve.

Notice a convex lens converges the light rays. (lenses work opposite of mirrors)

Again, convex lens = converges

However, a concave lens will make the rays diverge.

DIVERGE (“divide”) Converge (“collide”) Did you learn these words in the Earth Science done in 7th grade with Plate Tectonics ?

Watch what a change in angle does in a triangular prism. This allows rainbows to form. (∆ means “change”)

R O Y G B I V Red wavelengths with low energy, change direction the least.

Raindrops will act like a prism and mirror, making rainbows. So will diamonds, and this is why diamond cutters make so much money!

No change in direction when the incoming ray Light rays refract when they enter a medium with a different density (the light actually changes speed causing the change in direction). No change in direction when the incoming ray is perpendicular (90°) to the surface.

Why was Tom Hanks so bad at spearing fish in “Castaway”? (he didn’t know about refraction !)

Is this fish actually SPITTING ?! Sure is… It’s an “Archer fish”. It’s shooting at a bug that’s out of the water but it’s eyes are under the water. BIG PROBLEM !! Can a “stupid” fish do trigonometry ??

Compensation needed ! Shoot straight ! “SMART FISH” !

Remember, if the bug is perpendicular, there’s no angle change (shoot straight), but if there’s an angle, the fish has to compensate.

Here’s a good (and dangerous) example of refraction… a desert mirage! (imagine you saw water). The object appears much closer than it really is because air with different densities acts like a lens!

You can’t even trust where the Sun really is! The change in density of the atmosphere acts like a lens.

Refraction of sound waves is used for underwater mapping. Warm, less dense water reflects the sound waves differently than the deeper cold water.

This is a cool “Over / Under” photograph.

You’ve all seen this one: Refraction In Action !

When does light not follow a straight path? When there’s a massive “gravity well” in the way! like the yellow star below with a huge super-star or galaxy in the way. This is called a “gravitational lens”. End show