EM Waves 03


  • Blue light has a wavelength of about 450 nanometers. What is the frequency of that light? <GO!>
  • Radio Station 99.9 KISW (Seattle's BEST Rock!) broadcasts at a frequency of 99.9 megahz. Calculate the wavelength of their radio wave.


LEARNING TARGET: I will be able to explain why there are so many radio frequencies identified for our use during today's class..


  • hertz (Hz): a measure of frequency in waves/second
  • electromagnetic waves (light waves from radio - gamma)
  • quantum jump
  • energy levels
  • excited (electron) = ("electrons 'jolted' into a higher energy level")
  • rest state (electron) = ("electrons existing on the lowest energy level")


  • c=λυ: The speed of light (c) = wavelength (λ named "lamda") x frequency υ named "nu") Physicists LOVE to use greek letters... get used to it!



What is this? GXUVIMR



Those letters are our Rowdy Martians mnemonic written in order from highest to lowest energy/frequency (and therefore from lowest to highest wavelength)


What would happen if a REALLY powerful radio station started broadcasting at, oh, I dunno 99.9 megahz frequncy in Tacoma?



Don't you think it just MIGHT interfere with THIS?

What kind of problems does that lead to?

How do we keep that from happening?


Here's a fairly basic/common chart of the EM spectrum. Notice that each part of the


spectrum takes up roughly the same amount of space... that sorta kinda indicates that the EM Spectrum is divided up pretty evenly... yay?

Here's an EM chart that shows a much more exhaustive description of the RADIO part of the EMF spectrum... Notice how much larger the RADIO part of the EM spectrum actually is:

Let's see if we can deciper those now:


But WAIT!!! There's MORE!!! Take a gander at THIS GONZO verion:

HOLD ON TO YOUR HATS... Check out the HONKER version by clicking on that image...

Now... just what in tarnation is this thing, and just WHY is it so important? Also, what part of the EM Spectrum (SPECIFICALLY) does this cover?

Have a conversation, then go do a wee bit of research.

Now it gets a bit tougher..... work with your group and see if you can generate ANY sort of google search that will get you additional information about ANY of those bands (This can be frustrating, but stay with it!)


REFERENCE DOCUMENT: HERE is the FCC Table that our graph is based upon

DOCUMENT #1: HERE is how scientists try to reserve/get allocated parts of the radio spectrum

DOCUMENT #2: HERE's what the British Astonomers have to say about THEIR allocations of the radio spectrum

Research Projects. Collaborate with your group to make a coupla Google Slides to address ONE of the following:

1) One of the most important frequencies in radioastronomy is the "21 cm" line.

  • Briefly describe why that "21 cm" line is so important IN YOUR OWN WORDS
  • Calculate the frequency of that wavelength
  • Go to our chart and see if that wavelength has been allocated for radioastronomy
    • check again
  • Explain why the 1430 mhz frequency range IS NOT allocated, but 1420-1427 IS allocated

2) Find another important science frequency as found in Document #1

  • Briefly explain IN YOUR OWN WORDS what branch of science that frequency relates to AND why it is important
  • Check to see if that frequency is actually allocated to that branch of science
  • Check to see if similar frequencies are actually allocated to that branch of science

3) Find a radio freqency important to radioastronomy in Britain (See Document #2)

  • Briefly explain IN YOUR OWN WORDS why that frequency is important to radioastronomy
  • Find that same frequency on our chart and see if it is allocated there as well.
  • See if their are similar frequencies allocated on our chart for that type of radioastronomy



Let's investigate how each type of electromagnetic energy is created here on Earth. Since we've talked at length about visible light, we'll exclude that. A couple of these are *very* very tough.... but since I am your mg&hpi I'll wait to tell you.

Group 1 = Rowdy

Group 2 = Martians

Group 3 = Invaders

Group 4 = Users

Group 5 = Xrayers

Group 6 = Gunners

You have approximately 20 minutes to make a sketch with no more than 5 one sentence bullet points. Additionally, each bullet point can be no more than 12 words. Make sure your sketch is ready for prime time.

Time allocation:

  • 5 minutes sotto vocce work
  • 5 minutes collaboration with your group
  • 5 return to sotto vocce
  • 5 minutes collaboration

CITE YOUR SOURCES - (writing the URL is fine)

No wikipedia

No yahoo answers

No ask.com

No answers.com



Wanna Hint?

  • User Google Advanced Search to ONLY search nasa.gov or hyperphysics.com or similar sorts of sites