## Day 140 – Wave Interference

Physics 11 – The main goal for today was for students to investigate wave interference and standing waves. However, I started the class off with some voting questions using the wave equation. As you can see above, this was not time wasted. Everyone clued in on the second round of voting and could explain their mistakes.

I’m using distributed practice for the wave equation. Students have done a bit of practice over 3 days. I still haven’t given them a worksheet on it. Maybe we’ll get to this next class. By the time they are quizzed on it, they will have practiced this equation/idea over 3 classes with each class spaced over 2-4 days apart.

Physics 11 – Today students explored waves with Slinkies.  They looked a properties such as amplitude, frequency and speed, as well as generating both transverse and longitudinal waves.  Students played with making waves will recording video on their phones. This allowed me to speak with each group individually and check their understanding of the wave properties.  All in all it was a pretty relaxed class but our goals for the lesson were achieved.

## Day 144 – Peer Instruction on Doppler Effect

Physics 11 – One topic we (un)covered today was the Doppler Effect. We used peer instruction to help with understanding. Normally in all of my classes it’s like pulling teeth to get students to stand up, walk around and discuss questions.  For today’s question I told the class that everyone would get 800 bonus points if over 80% of the class got the correct answer. The catch was that I would randomly pick one student to give their explanation, so just sharing the answer would not be enough.

The funny part about all of this is that our grading system doesn’t work on a points system and they know this.  Everything is compared to standards and learning objectives.  So “800 points” is a meaningless term in my classes. I had to take a photo of this because you’ve never seen a class so invested in learning about a concept. I couldn’t help laugh and a few students caught on to my “800 points” trick and rolled their eyes.

## Day 130 – Mechanical Waves

Physics 11 – Students were introduced to mechanical waves today. The above three gifs are always a good starting point.  Lots of the things we touched on were a review from Grade 8 science, but that allowed us to move through these concepts pretty quickly.  The kids also had their last quiz on momentum today, no pictures required to imagine what that looked like!

## Pseudo Day 113 – Speed of Sound Lab

Physics – April 29

Students were asked to investigate the speed of sound by measuring standing waves produced in PVC tubes.  I asked them to try at least 5 different frequencies using tuning forks or apps on their smartphone.  The could then graph wavelength vs 1/frequency and the slope should be the speed of sound.

Unfortunately the lab just doesn’t work very well.  The room gets very loud with sound, and higher frequencies get the students really confused about wavelengths because of the different modes.  They don’t know if their tube length is 1/2wv, 3/4 wv, etc.

I really don’t know what I will do about this next year.  Maybe I’ll just go back to “let’s try this out to confirm the speed of sound!”.  I also tried on my own to vary the water/air temperature to come up with an equation for speed of sound vs temperature.  I was using my Fluke thermocouple inside the tube which gives a good reading of the air temperature, but the data was terrible.  Cold air had the slowest speed, warm air had the fastest speed, and hot air was in between. I think the air is not reaching a stable temperature inside the tube.

## Day 71: Creating and Analyzing Waves

Science 8 – Grade 8 science is starting a unit on waves and optics.  One of the first activities we covered was drawing a traverse wave using a vibrating marker pen drawing against a file folder that is moved horizontally.  I think the students really appreciated this lab, as it was quite surprising to them that a curved wave shape could be created by two perpendicular movements.  It also reinforced the concept of particles moving in one place (the marker) while a wave seemed to move along.

One extremely pleasing part of the lesson was when the student in the yellow volunteered to go first in presenting his whiteboard.  This student is interested in science but is shy at times, and maybe even lacks a bit of confidence. However, he was randomly put in a group where he became a natural fit for leading the group.  Not only did he show leadership in developing the group’s solution, but his willingness to share with the class was great to see.

Three excellent gifs are also used in this lesson: