Optics, reflection, refraction, total internal reflection

 Monday began with Bill Nye the Science Guy's Light and Optics done from a DVD player and HDMI cabled into the Smarttech 6075S-V3-p SMARTboard. Wednesday I ran the laser demonstration of reflection, refraction, and total internal reflection.


Thursday morning I stumbled into an empty aquarium. I would eventually fill the aquarium to the very top, along with various beakers and graduated cylinders. This makes the top of the container the top of the water and avoids the error students make of measuring to the top of a partially filled container. 


The aquarium also provided a nice display of total internal reflection.


I started with one plastic basin before I remembered I also needed an empty one.


The objects were harder to see in the clear container, the white dish basin provided a better backdrop. I eventually put a towel on the faucets behind the containers to help reduce ambient light glare off of the surface of the water. 


Halia, Ashlen, Serjean, and Sharla working on reflection


Jonathan and Jarret make reflection measurements


Jarret indicates the location of the image, Jonathan measures


Mersayes and Serjean enter data into Desmos


A penny in the aquarium. When filled to the brim, emptying the aquarium is challenging. I soaked myself in the process of emptying the aquarium at the end of the second session.


Here one of the beakers is filled to the brim.


This graduated cylinder was also filled to the brim. Sharla makes a measurement while Serjean holds the meter stick.


Ashlen and Mersayes

Ashlen, Serjean, Mersayes, Sharla


The two container set up by class end, the towel just visible at the upper right.


Left board after 8:00 class.


Right board


Kaylem and Fiji in the 11:00 section


Harvey, Shane

Rizal and Ozimy work on mirror measurements


Harvey, Thevonna, Billy, and Polly Melina


Melina adjusts the object

Harvey and Thevonna

Distance measurements for reflection really have to go from near zero to as far as possible. Students tended to clump measurements in a small range above 20 cm and below 40 cm. This can lead to a non-zero y-intercept which in turn can push the slope away from one. 

The same is true for refraction: the absence of small containers generated y-intercepts away from zero and led to larger errors in the slope. Filling all to the brim is actually a useful approach, each container a different measurement. Perhaps only a single tall graduated cylinder? Use as many other containers as possible to make up for the loss.

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