Electromagnetic Energy

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. ? ?

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

7. Radio waves • Longest wavelength EM waves • Uses: • TV broadcasting • AM and FM broadcast radio • Avalanche beacons • Heart rate monitors • Cell phone communication

8. Microwaves • Wavelengths from 1 mm- 1 m • Uses: • Microwave ovens • Bluetooth headsets • Broadband Wireless Internet • Radar • GPS

9. Infrared Radiation • Wavelengths in between microwaves and visible light • Uses: • Night vision goggles • Remote controls • Heat-seeking missiles

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

11. Ultraviolet • Shorter wavelengths than visible light • Uses: • Black lights • Sterilizing medical equipment • Water disinfection • Security images on money

12. Ultraviolet (cont.)

13. X-rays • Tiny wavelength, high energy waves • Uses: • Medical imaging • Airport security • Inspecting industrial welds

14. Gamma Rays • Smallest wavelengths, highest energy EM waves • Uses • Food irradiation • Cancer treatment • Treating wood flooring

15. 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

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

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

18. 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, 6.626 x 10-34 J/Hz v: frequency of the wave

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

20. 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

21. 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.

22. 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

23. 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

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

25. 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

26. 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.

27. What do you notice?

28. 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

29. Image credits • http://www.antonine-education.co.uk/New_items/MUS/images/Making6.gif • http://www.geocities.com/researchtriangle/campus/6791/einstein12.jpg • http://abyss.uoregon.edu/~js/glossary/wave_particle.html • http://www.astro.princeton.edu/~gk/A402/electromagnetic_spectrum.jpg • http://science.hq.nasa.gov/kids/imagers/ems/radio.html • http://www.nentjes.info/Palace/radio-6.gif • http://www.mobilewhack.com/motorola-h12-bluetooth-headset.jpg • http://www.stuffintheair.com/radar-real-time-weather.html • http://www.imaging1.com/gallery/images/AV%20Night%20vision%20goggles.jpg • http://www.global-b2b-network.com/direct/dbimage/50329753/Study_Remote_Control.jpg • http://www.georgiaprismaward.com/The_Prism_Story_files/PRISM%20brand%20imagemed.jpg • http://science.hq.nasa.gov/kids/imagers/ems/uv.html

30. Image Credits • http://farm3.static.flickr.com/2385/2381723771_12548f4bd1.jpg?v=1217429879 • http://intamod.com.au/images/uv2.JPG • http://science.hq.nasa.gov/kids/imagers/ems/xrays.html • http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/see_through_body/sci_media/neck_x_ray/17945-5-eng-NZ/neck_x_ray_full_size_portrait.jpg • http://www.epinion.eu/wordpress/wp-content/uploads/2008/05/airport-security1.jpg • http://science.hq.nasa.gov/kids/imagers/ems/gamma.html • http://www.aboutnuclear.org/print.cgi?fC=Food • http://www.roswellpark.org/files/1_2_1/brain_spinal/gamma%20knife%204c.jpg