### Reflection and refraction

This term I did the refraction demonstrations on Wednesday, including the placing of a one dollar coin on top of a towel and under a beaker filled with water. The top of the beaker was covered with a ceramic floor tile. I then asked the class to come up and determine what coin was under the bottom of the beaker.

Due to total internal reflection at the bottom, and refraction at the sides of the beaker, the coin is invisible.

Then I put the coin in an empty frisbee on the table. From the other end of the table the students could not see the penny. Then I added water until the frisbee was full. The penny could now be seen.

I wrapped up Wednesday using the laser and running it through a semi-circular dish of water. I did also try to shoot the laser through a plastic tube filled with water - not very successfully. Then I tried to get the laser to run inside the water cascading out of a hole in a 5 gallon water jug. Other than making the floor wet, I accomplished little. I need something more sophisticated to demonstrated the fiber optic total internal reflection effect.

I also demonstrated the image forming ability of convex magnifying lenses.

Moving the demos up to Wednesday worked well for keeping the laboratory focused on the image and object distance relationships. Works better than having these on Thursday. What was sacrificed was the optics lecture with coverage of hyperopia, myopia, presbyopia. This term was also the first term that I showed Bill Nye's optics DVD. It is somewhat scattershot, maybe too scattershot to be useful. On the plus side the DVD did set up the Wednesday demonstrations. Not sure if I should again use that DVD.

Measuring the apparent depth of a penny under water to determine the index of refraction of water.

LoriAnn and Tulpe determine the apparent depth. This laboratory still leads to a

Ashley measures the object distance for a figurine.

Rose Ann.

Emily, Eugene