Thursday, January 14, 2016

A really cool science lesson

This week we are learning about light and waves. We haven't taught this in a couple of years because we just haven't had the time with all of the state testing and furlough days.  This year there isn't money in the budget for testing days and we got our furlough days back last year, so we have a few extra days of actual teaching.  We've rearranged some things in the schedule and so I'm having to come up with some new lessons.

A couple of the new teachers did a demonstration of measuring the speed of light using a microwave oven and some marshmallows.  I'm not one for doing things for the kids.  I like the kids to do the science and have the experience for themselves, so I started working on changing the lesson around so the kids could do the experiment and come up with the answer themselves.  It took a couple of days of playing around with things and searching on the internet, but the lesson I came up with (with the help of a colleague) was better than I had hoped.

We used marshmallows set in a line on a piece of paper along the bottom of a microwave.  You have to take the turntable out of the bottom.  I remember way back to when we got our first microwave.  It didn't have a turntable and the food would not heat evenly.  There was a heating element in the top that looked like a stirring whisk.  I remember my brother was little, maybe 5 or so and he asked why the stir-er wasn't working.  He thought it was supposed to come down and mix the food.

Anyways, you remove the turntable so the paper stays in place.  There are natural hot spots in the microwave that will show you where the nodes, or crests and troughs on the wave are.  You use that to calculate the wavelength and then using the formula for speed, multiply the frequency of the microwave (which is 2450 MHz).  The coolest part about the experiment was about half the students laid their marshmallows out in a straight line and cooked them for 10 seconds and when they pulled the paper out with the marshmallows on it, the marshmallows had moved into the shape of a sine curve.  It was really neat to see how the heating caused the marshmallows to form into the wave on the paper.  Only the students who actually followed the directions go this result, so if they put the paper in crooked, or pushed it too far back in the microwave, it didn't work.

Then, after doing the calculations, the kids got to eat the marshmallows.  I think they will remember this lesson better than if I had just told them light goes really fast.

My daughter who attends UCLA said her friends said they really didn't do many experiments in high school.  She said she really feels like she learned a lot by doing so many experiments and hands on activities.  I'm glad that I teach in a school that allows for these kind of things and allows me to play most of the day.  Even though sometimes the money for supplies does have to come out of my pocket.

I was really hoping to win the super lotto last night.  I had great plans on how to spend it.  I guess I will just have to keep going back to work.  At least I enjoy what I'm doing most days :)  I mean where else do you get paid to cook marshmallows in the microwave or soak potatoes in sugar water and figure out the concentration of sugar in a potato cell?

1 comment:

Sue Niven said...

I think I would have liked to have been a kid in your school. There is nothing in the world that can compete with hands on experiments. Well done!