Science Day #1 - Fun with Microwaves

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Next we tried arranging licorice sticks in a grid.

It worked better than the marshmallows, but that isn't saying much.

Burning licorice generates a foul odor and tons of smoke.

Matt tried a piece of charred licorice. You can't tell from his face, since that's the only face he ever makes, but he wasn't impressed.

We tried putting the licorice in at angles radiating out from the magnatron, the part that generates microwaves, which is in the corner of the machine.

It sorta worked. The nodes are the uncooked bits of licorice, shown by the arrows. They represent nodes at half-waves, so you can find the speed of light by this equation:

c = 2 x D x f

where D is the distance between the nodes and f is the frequency of the microwave.

George was starting to get bored again.

We weren't satisfied with the licorice nodes, since it was too hard to find the wave pattern. Someone had the idea of smearing pancake batter over the bottom of the dish, and then seeing where it cooked. That way, we could see exactly where the nodes and antinodes were, and thus calculate the speed of light.

This is the plate after two minutes. The pancake batter worked perfectly! We'd calculated the speed of light with a 0.00% error!

After a couple minutes, we could see our heinous plan coming to fruition.

Perfect! After about six minutes, the quarter-inch pancake showed the wave pattern perfectly. The dark spots are the antinodes, and the light spots are the nodes. The two we're using are where the wave pattern is clearest, emanating directly from the magnatron, which would have been at the top of the picture.

There was a slight disagreement about the proper procedure for measuring the node distance. John wanted to use his engineering rule, and I wanted to use my art ruler.

There is only one way to settle a scientific dispute: A fight to the death!

The distance between the nodes was about 6.7 cm. The frequency of the microwave was 2450 Megahertz.

Our calculated speed of light was 3.28e8 meters per second.

The actual value according to google is 299 792 458 meters per second. We were off by a mere 9.5%, which isn't bad considering we did it with pancake batter and a $25 craigslist deal. We were probably off because the microwave doesn't create a perfect wave pattern, with exact nodes and antinodes. It's like a room that isn't acoustically perfect-the waves interfere with each other and the signal gets muddled.

The pancake was so hot, it melted my shoddy plastic ruler. I guess John was right.

Continue reading part 3

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