Reflection and refraction

 Monday was a holiday this week, thus Wednesday was used to introduce reflection and refraction. I opted to use the laser to demonstrate diffuse and specular reflection. Then I used the water tanks to demonstrate refractive effects. This term I included a hand waving introduction to n₁sin₁=n₂sinθ₂. After demonstrating refraction through a prism, I covered convex lenses and image formation. The class wrapped up with a visit to a fish tank.

The class opened with an introduction to the coin in the basin. I should also introduce the disappearing test tube, but I need a heavy vegetable oil to pull that off.

The board introduction for the two legs of the laboratory.

Marcia and Derisalyn

The graduated cylinders are at the edge of the table to enable measuring down from the surface of the water. Explaining the procedure as a measurement down from zero at the water surface reduced the tendency to accidentally measure up from the bottom to the image position of the penny. Still, one afternoon class pair measured up to the apparent penny location.

Cynthia estimates the apparent depth

Mercedes sets up to work on apparent depth measurements

Josephine measures the object distance from a plane mirror

Josephine and Cynthia

Lailani, Marcia, and Derisalyn

Lailani and Mercedes working on reflection data

Derisalyn. Selfie session.

Post-class board

Group discussion of results and status of Derisalyn and Cynthia's theories for the slope

Melrose explains the laboratory to Stephie and Johannes

Melrose locating the image position

Mikie gettting ready to measure apparent depth

Destiny Grace and Keiko-Lalii "Krena" work on apparent depth, Herna records data

Destiny and Keiko-Lalii

Mikie makes measurements while Melrose records

Johannes joined the midday section and worked with Stephie

Johannes handled the image locations, Stephie recorded data

Herna locating the image

Destiny Grace, Keiko-Lalii Krena, Herna

This laboratory, while basic, continues to serve its purpose. At this point in the term the students are able to render their own mathematical models, and yet there is a naivety to their models, such as o₁ ~ i₁ which lacks any degrees of freedom and has a slope locked in at one. Thinking mathematically is far harder than one who can think mathematically might imagine.

A rainy Friday prevented being able to go out and look for a mirage. Along with some mirage videos, I did do a demonstration of the disappearing test tube. Turns out the smallest test tubes, which have a plastic-like feel, did not work well. The glass test tubes worked the best. The palm oil, while cheap and readily available, was perhaps suboptimal. Lighting also plays a role - avoid back lighting. I used a mix of 600 ml and 400 ml beakers, the oil was a liter bottle of palm oil.