Today, groups whiteboarded one of the three graphs that they prepared last night for homework. They presented how they used it to find the half-life of the sample and we compared and contrasted different approaches and different graphs by different groups. The aggregated data from two classes was great:
One group realized that the area under the plot of number of “nuclei” decayed in a given roll vs. time was the total number of nuclei decayed. They integrated the function that fit the graph to find the half life.
This year, we used our new collection of dice to perform the half life lab instead of M&Ms. Over the two classes, we aggregated over 1100 rolls. For homework, students will plot the aggregated data in three ways: number of “nuclei” remaining vs. time, number of “nuclei” decayed in a given roll vs. time, and ln(number of “nuclei” remaining vs. time). They then will use each graph in some manner to determine the half-life of the sample.
The Chromebook once again demonstrates its flexibility:
Today, we started our final chapter of the year. I absolutely love how binding energy problems are easily solved and presented using energy LOL diagrams where mass is simply another energy storage mode.
I’ve started using Socrative for assessing students’ short response answers. It serves a couple of purposes. One, I gain valuable insight into what each student does and doesn’t understand. Two, students see each other’s responses, critique them, and see examples of strong responses. Today, one of the questions I posed was from Knight’s College Physics: “The n = 3 state of hydrogen has E3 = -1.51 eV. Why is the energy negative? What is the physical significance of the specific number 1.51 eV?”
The responses clearly demonstrated that there was a substantial number of students who attributed the 1.51 eV as the difference in energy between the ground state and n=3 instead of the difference in energy of the electron between n=3 and infinity.
If I had asked someone to volunteer and answer the question, I never would have realized how few students understood!
Today, AP Physics 2 students whiteboarded a series of problems concerning spectra. While a conceptual understanding of energy levels and spectra are necessary, most of the problems concerned conservation of energy. I was pleased that some groups even drew energy LOL diagrams on their whiteboards!
Today, there were only two or three juniors in each of my AP Physics 2 classes. We worked on practice problems together. Seniors had various senior activities, including an assembly where a small portion of the class get hypnotized. It is amazing and hilarious!
Today we sought to answer three questions:
- Why do different elements have different spectra?
- Why is the absorption spectra a subset of the emission spectra for an element?
- Why don’t electrons give off energy and spiral into the nucleus?
I also shared how spectra is a critical tool in astronomy so students appreciate this phenomenon.