Co-op Science Week 12

Continuation of light and optics.

We started off by playing with a set of spinning top optical illusions I'd found at Hobby Lobby.  It included Benham's top, a spiral that produced the waterfall effect, and some disks that worked better under fluorescent lights.  We discussed briefly why these things appear the way they do; I included the information that scientists don't know everything about these illusions, so the kids could maybe discover more about them some day.

Next, discussion:

What produces light?  (Sun, lightbulbs, flames; the moon simply reflects rather than producing)
What happens to light? (travels in a straight line forever unless it hits something)
What happens when it hits something?  (sometimes passes through whatever it hits; may convert to heat or other energy; may bend)

While talking about these things, did the demo of shining a flashlight through index cards to show this concept (although I just cut notches in the bottom of mine instead of punch holes -- directions in Super Science Projects about Light and Optics by Allan Cobb).  Answered repeated queries as to whether we could set the modeling clay on fire with a firm "No".

Vocabulary words:  Opaque, transparent, translucent.  I broke these down into their roots.  Mostly I was surprised that some of the kids didn't know them.  Shone flashlight on cardstock, copy paper, and through glass.

More vocabulary:  reflection, refraction.

For reflection we talked about mirrors, and how the light bounces off at the same angle it hits.  I had made  a shoebox periscope using cheap little mirrors from the craft store (Hobby Lobby?  Michael's?) and a bunch of duct tape (by the way, it was amazingly tedious to get the mirrors lined up correctly).  Pretty much everyone was familiar with the concept, but no one had actually made one before.   Again, I used the directions from Allan Cobb's Super Science Projects about Light and Optics We shone the flashlight through it, we used it as a periscope, we shone a laser pointer through it.  I had to keep moving one kid's head since he seemed determined to have the laser pointer reflection go right into his eye in spite of my saying we were NOT going to point it into anyone's eyes.

Speaking of which, Rick loaned me his nice red laser pointer he uses in presentations -- one of the nice, expensive ones.  He has a friend with one of the green ones, which would've impressed the kids immensely, I'm sure, especially since I told them that in many places it's illegal to shine them up in the sky at night, and that you can't even take them into some countries.  As you can imagine, the set-the-clay-on-fire, shine-the-laser-in-the-eye crowd instantly realized that their deepest desire was to obtain strong laser pointers and shine them in the sky.

For refraction, I drew a picture on the board of a bird's eye view of all of them holding hands and running in a straight line; the line was at about a 45 degree angle to a body of water.  As the first kids got to the water they had to slow down since it's harder to run in water than on dry land ... eventually, the line looked bent.  I got this analogy from Vicki Cobb's Light Action, which is a book  I would highly recommend if you're explaining this stuff to kids.

We refracted light with water .  I put a coin in the bottom of the bowl, had everyone stand where they couldn't quite see the coin, then filled the bowl with water; the penny appeared (I'm pretty sure this same demo is one of the experiments in Apologia Physical Science).  Then I placed a penny on the table, put an empty glass on top of it, filled the glass with water, set an index card on the top of the glass (so we couldn't look straight down into it) and the penny was invisible.  This one really confounded one of the kids, who thought I'd done something or other with the penny even though he was watching every thing we did.

We also shone the flashlight through plastic prisms (purchased cheaply at Hobby Lobby) to bend the light and see a bit of a rainbow.  It was a gloomy day, so we couldn't use sunlight to make better rainbows, unfortunately.  Again, all of the kids seemed familiar with the concept, but they enjoyed messing around with the prisms.  And we shone the laser pointer through the prisms, too.

Finally, we made Movie Wheels.  I had shown one I'd made to some of the kids the week before when we made thaumatropes.  They were surprisingly enthusiastic about this.  Well, most of them were.  One boy wanted to play with the tops -- we had him sit at a different table, and he eventually started making some rather sophisticated paper airplanes.  Another wanted to make it, but wanted someone else to do the work -- pretty funny.  We have a mirror in the room, so they could view them in there or else stand in pairs and view each others'.

A few of the kids said they'd studied all of this before, but they are enjoying studying it again.  That's what we're after -- a hands-on supplement to the curriculum they're doing at home.