03/20 Wheeler

Today, March 20th, is a rather exciting blog day for me. Why? Well, first off, I always find something cool or exciting about the blog. Second, this is only my second blog on a non-test day! So, I get to explain the fantastic physics we learned today, not just describe how we scribbled with pencils and punched numbers into the calculator the entire period, all the while stressing if number seventeen is correct. For Coats-Haan's sake, I hope our test-taking doesn't look as boring as the sophomores during OGT week.

We turned in the Shockwaves Worksheet (if you did not finish it yesterday) and we checked page 507, numbers 70-76 in our physics book (which could stand to lose some weight, I might add). Coats-Haan piped in at this time to remind Chris Roseblossom he needs to get off the streak of not doing homework, reminding him that he was one of the smartest, laziest kids she knows. I agree with that statement. Also, keep in mind that our exams are next week! So, working on the 3rd quarter exam review is not a bad idea.

I rather liked today's notes. There were only twelve slides, I believe, either way not enough to make my hand hurt. We learned the difference between intensity and loudness. Intensity is the rate at which the sound energy flows through a unit area normal to the direction of propagation. Loudness (or volume, as the slides pointed out) depends on an auditory sensation in the consciousness of a human listener and isn't quantifiable.

Okay, so here are a few more handy equations we learned in class today. Try to make some room in your brain for a couple more, okay? We are three fourths of the way through the year. We can do this!

Intensity = Power/Area
Or, the shorter version (aka Chris Roseblossom's version), I = P/A
P is in watts, A is in square meters, and I is in watts per square meter.
The normal area is the surface area of a sphere, 4 times pi times radius squared (hello, old friend geometry!).

B = 10 log (I/I_o)
I_o = 10^-12  watts per meter squared  
B is the relative intensity in decibels

Recalling those log properties we learned (again) a few months ago in honors pre-calc might also do you some good.

For homework, we have to complete the pair check (if not finished in class) and do two worksheets, one titled "Loudness and Intensity Homework" (I would have never guessed) and the other "Detecting Decibels/I've Got Your Frequency."

And finally, to answer the question of the day. Because of the large range of intensities over which the ear is sensitive, we use the logarithmic scale.