## Day 124: Measurement and Analysis Assessment

I was at the NSTA National Conference in Chicago today. My students did something different while I was gone. My colleagues and I have been working on a series of measurement and analysis assessments. We plan to administer these to the AP Physics 1/2/C classes and track how students do throughout the year and from year to year. We defined the following standards:

1. Retrieve quantitative data from an experimental source and organize it in a data table denoting; units, dependent/independent variable.
2. Properly plot data and determine type of fit, fitness of fit, establish mathematical model with proper units.
3. Properly analyze and make sense of the slope and intercept of the derived mathematical model.
4. Apply the model to a different situation.

For the first assessment we used the Direct Measurement video of the Ping Pong Cannon.

##cvpm

## Day 123: Photoelectric Effect

Today was much better than yesterday. For the second year, I used the bridging activities in Randall Knight’s Five Easy Lessons for the photoelectric effect. We started with a simple resistor circuit, moved to a thermal emission diode, and finally introduced the photoelectric effect. After each, students sketched current vs. voltage graphs.

##modern

## Day 122: Quantum Effects Demos and Discussions

Today was not the best day of AP Physics 2. At first I considered some sort of a paradigm lab involving solar cells, but after trying various equipment and light sources, I couldn’t come up with something effective. If anyone has a good introduction activity for the photoelectric effect, please let me know!

Instead, I ended up with a series of demonstrations that I hoped would provoke good discussions. We observed various amount of current produced by a solar cell based on the intensity of the incident light. We also observed how the solar cell could like a red LED but could not light a blue LED regardless of the intensity. We observed fluorescent chalk under a UV light. We asked a bunch of questions which we will answer over the next several days. I wish I had a zinc plate to attach to an electroscope to demonstrate the photoelectric effect.

Not a great lesson, but a few good questions raised.

##modern ##setbacks

## Day 121: Geometric Optics Exam

Today, AP Physics 2 students completed the optics unit with the geometric optics exam. Based on first impressions, we should have practice ray diagrams more than we did. It’s hard to know with the new course how much to emphasize different areas. We didn’t solve any dual-lens problems at all. Based on my interpretation of the Essential Knowledge and Learning Objective statements, I think this is a reasonable decision.

##optics

## Day 120: Determining the Thickness & Refractive Index of a Mirror Practicum

Today, I tried a new lab practicum based on The Physics Teacher article, “Determining the Thickness and Refractive Index of a Mirror.” Through careful measurements of the reflected and refracted beams and graphical analysis, students determine both the thickness of the mirror and the index of refraction. The most challenging part of the lab was keeping everything aligned and accurately measuring the angle. The use of the level app on a smartphone made measuring the angle much easier. My first class struggled to make accurate measurements as we were trying to keep the laser level and angle the mirror and screen. After watching one group during first hour try various techniques, I encouraged second hour to take a different approach. They changed the angle of the laser and left the mirror flat on the table. This approached resulted in more accurate measurements.

##labpracticum ##optics