Day 141: Half-Life Plots

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:

Radioactive Decay Simulation with Die Rolls

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.

  ##nuclear  

Day 140: Half-Life Lab

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:

IMG_2564

  ##nuclear  

Day 138: Using Socrative for Short Response Questions

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.

Screen_Shot_2015-04-24_at_9_01_40_PM

If I had asked someone to volunteer and answer the question, I never would have realized how few students understood!

  ##modern ##tech  

Day 135: Spectra

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.