And More Rain

I am considering building an ark...I already have two dogs...

Honors Physics discussed yesterday's lab and any discrepancies in data that they might have noticed. We then went over the homework questions/problems and the open-book vibrations and waves quiz. Finally, it was time for new material and that material was harmonics. For musical instruments, harmonics produce the characteristic sounds on instruments and the overall quality of the sound. The overtones for the tuning fork that you documented in your lab were harmonics of the tuning fork's fundamental frequency. Stringed instruments and pipes open at both ends are able to produce a full harmonic series. Pipes closed at one end are restricted to the odd harmonics. Additionally, these instruments have, for their fundamental frequencies, corresponding wavelengths that are 4x the length of the vibrating air column. The stringed instruments and pipes open at both ends have wavelengths for their fundamental frequencies that are 2x the length of the vibrating media. The difference is that for strings and open pipes, each end of the vibrating material is identical - both nodes or both antinodes. For a pipe closed at one end, one terminus is a node and the other is an antinode. Be sure to have these distinctions well in mind for next week's test. Tomorrow - beats!

Physical Science B examined mirrors. Plane, convex and concave - mirrors rely on reflection for image formation. Plane and convex mirrors only form virtual images but concave mirrors can form both virtual and real images. Students had the chance to handle each type of curved mirror and examine a large convex mirror that had been used as a security mirror. A little bit of color was discussed, but more of that will be had during tomorrow's film and in class on Monday.

Physical Science E watched their light and color film - fairly basic but covered all the high points. We will review the basics of light and color tomorrow and begin to discuss another behavior of light - refraction. On Monday, you'll conduct a few lab investigations on properties of light: reflectivity, polarization and intensity.

Physics F spent time finalizing their discussion of sound. The concept of harmonics was defined and harmonic series for various types of instruments was discussed. The role of harmonics in producing the characteristic sound of different instruments was examined, as was the importance of harmonics in producing enjoyable music. Then, the phenomenon of beats was introduced - alternating constructive and destructive interference that can be used to determine how out of tune is a particular instrument. Tomorrow, a series of lab investigations on properties of sound.

Physics G conducted their sound lab investigations today. The speed of sound was determined for room temperature air and for heated air. Then, the sound profile for tuning forks, the human voice and a computer-generated tone dialer was examined. Tuning forks produced fairly clear sine curves when lightly struck and more complex waveforms when firmly struck. This was due to the production of overtones (harmonics). The audio profile for the human voice was also complex. Humans do not emit a single note when they speak or sing, there are other tones blended in that were demonstrated on the computer. The tone pattern for the tone dialer is designed that each number is represented by two tones: a row tone and a column tone. In this way, note frequency combinations generate numerical information for the phone company. Tomorrow, we'll discuss the lab and take time to more closely examine those overtones in our discussion of harmonics.

Homework

Honors Physics A: None
Physical Science B: None
Physical Science E: Chapter Review items #22-25 and p. 519 #1-3
Physics F: Read lab protocol sheet and complete Chapter Review items #29-38
Physics G: Complete lab write up