1. Lesson: Electcromagnetic Spectrum (EMS)

2. Parts of a wave
Wavelength – Distance between two corresponding points on successive waves.
Amplitude – measure of a wave’s “strength” (height of crest or trough).

3. The Wave-like Electron
The electron propagates through space as an energy wave. To understand the atom, one must understand the behavior of electromagnetic waves.
Louis deBroglie

4. Electromagnetic Wave – An electric wave and magnetic wave moving at right angles to each other.

5. Electromagnetic Spectrum – Arrangement of all forms of electromagnetic radiation in order of frequency and wavelength. 5

6. low frequency = long wavelength high frequency = short wavelength
Frequency (ν): number of wavelengths that pass a certain point in a given amount of time.
- units are Hertz (Hz)
If these 2 waves are traveling at equal speeds, which wave will have more wavelengths cross the finish line in one minute?
low frequency
= long wavelength
FINISH
high frequency
= short wavelength

7. low frequency = long wavelength high frequency = short wavelength
If these 2 waves are traveling at equal speeds, which wave will have more wavelengths cross the finish line in one minute?
low frequency
= long wavelength
FINISH
high frequency
= short wavelength

8. Left Side Practice
1) Pick a type of wave on the EMS (not visible light).
2) Draw a pic of that wave and label the crest, trough, wavelength and amplitude.
3) Write and answer these questions:
Does it have a greater wavelength than visible light?
Does it have a higher frequency than visible light?
Does it have more or less energy than visible light?

9. 3) Write and answer these questions:
Does it have a greater wavelength than visible light?
Does it have a higher frequency than visible light?
Does it have more or less energy than visible light?

10. Which has the greatest: Wavelength? Frequency? Energy?
Warm Up 10/17
Which has the greatest: Wavelength?
Frequency?
Energy?

11. All waves on the EMS travel at the speed of light (c).
c = speed of light = 3.00 x 108 m/s.
c = λ x f
Wavelength (λ) and frequency (f) are inversely related. c λ = f
to solve for λ … c f = λ
to solve for f …

12. Calculate the υ of a wave that has a wavelength of 5.00 x 10-6 m.
Practice
Calculate the υ of a wave that has a wavelength of 5.00 x 10-6 m. c ν = λ ν = = ν Hz
Does this radiation have a shorter or longer λ than red light?

14. Practice
What is the wavelength of radiation with a frequency of 1.50 x 1013 Hz? c λ = ν λ = λ =

15. On Your Own Practice
Calculate the wavelength of yellow light emitted by a sodium lamp, if the frequency of the radiation is
5.10 x 1014 Hz.
* Hint: Be sure you set up the right equation. Ask yourself: which variable am I solving for?

16. Create Your Own Problem
Create a problem so that you have to solve for frequency (f). To do that, just make up a wavelength (between and Solve it for yourself, then find one other person to solve it and check your work. Be sure to write your question as a word problem. 4
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