1. Electromagnetic Energy

2. Waves… a review Most waves are either longitudinal or transverse.
Sound waves are longitudinal.
But all electromagnetic waves are transverse…

3. ? ?
Prompt students to guess what the teal box, then the blue box, is hiding. (Wavelength, Amplitude)

4. Electromagnetic waves
Produced by the movement of electrically charged particles
Can travel in a “vacuum” (they do NOT need a medium
Travel at the speed of
light
Also known as EM waves

5. Wave-particle Duality
Light can behave like a wave or like a particle
A “particle” of light is called a photon

6. Clicking the little rainbow box at the top of each slide will bring you back to this one

7. Radio waves Longest wavelength EM waves Uses: TV broadcasting
AM and FM broadcast radio
Avalanche beacons
Heart rate monitors
Cell phone communication
Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

8. Microwaves Wavelengths from 1 mm- 1 m Uses: Microwave ovens
Bluetooth headsets
Broadband Wireless Internet
Radar
GPS
Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

9. Infrared Radiation Wavelengths in between microwaves and visible light
Uses:
Night vision goggles
Remote controls
Heat-seeking missiles
Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

10. Visible light
Only type of EM wave able to be detected by the human eye
Violet is the highest frequency light
Red light is the lowest frequency light
Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

11. Ultraviolet Shorter wavelengths than visible light Uses: Black lights
Sterilizing medical equipment
Water disinfection
Security images on money
There is one more UV slide…

12. X-rays Tiny wavelength, high energy waves Uses: Medical imaging
Airport security
Inspecting industrial welds
Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

13. Gamma Rays Smallest wavelengths, highest energy EM waves Uses
Food irradiation
Cancer treatment
Treating wood flooring
Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

14. Calculations with Waves
Frequency: number of wave peaks that occur in a unit of time
Measured in Hertz (Hz)
Represented by nu (v)
Wavelength: the distance between wave peaks
Represented by lambda (λ)
c= λv, c=3.0 x 108 m/s

15. Understanding Wavelength/Frequency
If the wavelength is longer, the frequency is low
If the wavelength is shorter, the frequency is high

16. Practice
A certain green light has a frequency of 6.26 x 1014 Hz. What is its wavelength?

17. v: frequency of the wave
Max Planck
Assumed energy was given off in little packets, or quanta (quantum theory)
He called these quanta photons.
He determined the energy of this quanta of light could be calculated
E=hv
E: quantum of energy
h: constant, x J/Hz
v: frequency of the wave

18. Practice
What is the energy content of one quantum of the light in the previous problem?

19. Bohr Model of Atom Proposes that the atom is “quantized”
As electrons move around the nucleus, they have specific energies
Only certain electron orbits (energy levels) are allowable

20. Bohr Model
Atoms are most stable when their electrons are orbiting around the atom with the lowest possible energies. This lowest energy state is the ground state.
If the electrons absorb energy, the atom can leave the ground state and jump to a higher energy state called the excited state.

21. Bohr Model
The electron jump (a quantum leap) occurs when an atom absorbs a packet of electromagnetic energy called a photon.
Only photons of certain energies are absorbed during this process

22. Quantum Leaps
Create a high energy state for the atom which is not favored by nature and is unstable
Electrons immediately release the energy that they absorbed to return back to ground state

23. Energy Released
The energy is released as specific energies of visible light which we see as different colors

24. Types of Spectra
Absorption (dark-line) spectra appear as a rainbow of colors with dark lines in it. Each dark line represents a specific amount of energy that an electron absorbs as it quantum leaps into a higher energy orbit

25. Types of Spectra
Emission (bright-line) spectra appear as a dark background with lines of color in it. Each colored line represents a specific amount of energy that an electron releases as it quantum leaps back to its original orbit.

26. What do you notice?

27. Analyzing Spectra
Analysis of the spectra of different substances is the basis for spectroscopy
The study of the energy which is given off and absorbed when atoms go from the ground state to the excited state and back again