Electromagnetic Spectrum

Recall that waves can be categorized into two major divisions:

Mechanical waves, which require a medium. These include sound, water and waves on a (guitar, etc.) string

Electromagnetic waves, which travel best where there is NO medium (vacuum), though they can typically travel through a medium as well. All electromagnetic waves can be represented on a chart, usually going from low frequency (radio waves) to high frequency (gamma rays). This translates to: long wavelength to short wavelength.

All of these EM waves travel at the same speed in a vacuum: the speed of light (c). Thus, the standard wave velocity equation becomes:

c = f l

where c is the speed of light (3 x 10^8 m/s), f is frequency (in Hz) and l (which should be lambda) is wavelength (in m).

HW

For C block - Go through your notes and generate a review page.

For E block - that will be your homework after Thursday's class. For tomorrow, make sure you did the Doppler problem creation already assigned.

Thanks!

Hw

Oops

I posted the homework (for E block) on the wrong blog - homework is to create and solve your own Doppler effect problem, with at least 4 parts.

This is the same hw as is due Wednesday for C block.

Thanks!

HW

C block - write and solve your own Dopper effect problem. It should have at least 4 parts, like the class example.

E block - same as earlier post. Find and interpret an equation for the Doppler effect.

Happy 3 day weekend!

Homework revisited

Doppler effect:

E block - find (and interpret) an equation for the Doppler effect

C block - define (formally) the Doppler effect and find an equation that represents it. Same as the previous blog entry.

Doppler Effect HW

Come to class with a working definition of the Doppler effect (equation optional).

Play with these applets:

http://www.lon-capa.org/~mmp/applist/doppler/d.htm

http://falstad.com/mathphysics.html

Run the Ripple tank applet -

http://falstad.com/ripple/

Homework

Practice for the upcoming quiz - which is class after next

1. Consider a string, 0.4 m long. The normal wave speed is 120 m/s. Find the wavelengths and frequencies of the first 3 harmonics. Draw the standing waves as well.

2. repeat the first problem for a tube open at both ends, if it is 0.8 m long and the speed of sound is 340 m/s.

3. Consider problem 2 - what would happen if the tube were capped on one end.

4. Consider a concert A - 440 hz. Find these frequencies:

A. The next 2 A notes
B. The note immediately after A.
c. The note 3 piano keys after A