This was the third day of the study of light and how it interacts with matter. While I did allocate more class time for the social studies project (mini-poster) as well as it being a literacy day, I still wanted to demonstrate the property of reflection. More specifically, I proved the Law of Reflection that states that light will always reflect a surface at the exact angle that it strikes it at. For example, if a beam of light hits a mirror at 90°, it will reflect outward at 90°. More on that below.
First, this being a Wednesday the students spent the first 30 minutes doing independent reading. While they were doing that, I worked with a small pull-out group.
Afterwards, I had them do the warm-up:
After that, I did two demonstrations. The first one was an experiment that they saw while watching Bill Nye the Science Guy episode yesterday. This one showed how light reacts with water. I punctured a hole in a one liter soda bottle closer to the bottom, taped the hole, and filled the bottle with water, screwing the cap on. Then, as the water poured out of the hole, I shined a green laser into the bottle near the hole on the opposite side. The laser light traveled through the pouring water and internally reflected through it.
The next demonstration was to prove the Law of Reflection in which a beam of light will always reflect at the exact angle from which it came. I filled a large, clear biscotti container full of tonic water. Tonic water has a powdery substance called quinine, which is the bark of a tropical tree that was traditionally used to treat malaria. In this case, tonic water is found where seltzer water and sparkling water are located in any supermarket.
The neat thing about quinine is that it reacts with light from the 405nm wavelength, which is violet. Shining a violet laser or simply black light will react with the quinine and fluoresce. I placed a protractor at the bottom of the container to show how it works. If you look carefully, you can see the protractor. I projected it onto the screen by using a document camera so that all students could see.
I then allowed the students to work on their social studies project.