A Walk Through the Electromagnetic Spectrum

1. A Walk Through the Electromagnetic Spectrum Ken Morgan ENGR302 May 7, 2002

2. The Nature of Light • Three paradigms… • Light as an electromagnetic wave • Light as a stream of particles (photons) • Light as a probability wave • Light isn’t just one of these; it’s all three!

3. The Nature of Light • Light is an electromagnetic wave In 1801, Thomas Young showed that light is a wave: Young’s double-slit interference experiment

4. The Nature of Light • Light is a stream of particles called photons The Photoelectric Effects

5. The Nature of Light • Light is a probability wave

6. The Nature of Light • Maxwell’s Equations or A time-varying magnetic field is a source of a time-varying electric field.

7. The Nature of Light • Maxwell’s Equations or The sources of a magnetic field are electric currents and time-varying electric fields.

8. The Nature of Light • Maxwell’s Equations or The only source that produces a nonzero flux through a closed surface are free charges.

9. The Nature of Light • Maxwell’s Equations or No analog of free charges exists for a magnetic field.

10. This does not exist by itself! The Nature of Light • Wave propagation

11. The Spectrum

12. Radio from space Radio • Wavelengths: ~ 100 km – 1 mm • Frequencies: ~ 3 kHz – 300 GHz • Energy: ~ 12 peV – 1.24 meV

13. Radio

14. Infrared • Wavelengths: ~ 1 mm – 698 nm • Frequencies: ~ 300 GHz – 430 THz • Energy: ~ 1.24 meV – 1.78 eV Anything above absolute zero gives off infrared radiation.

15. Visible • Wavelengths: ~ 698 nm – 400 nm • Frequencies: ~ 430 THz – 750 THz • Energy: ~ 1.78 eV – 3.1 eV

16. Ultraviolet • Wavelengths: ~ 400 nm – 1 nm • Frequencies: ~ 7.5x1014 Hz – 3x1017 Hz • Energy: ~ 3.1 eV – 12.4 keV

17. X-Rays • Wavelengths: ~ 30 nm – 0.03 pm • Frequencies: ~ 1016 Hz - 1022 Hz • Energy: ~ 40 eV – 40 MeV

18. Gamma-ray bursts Gamma-Rays • Wavelengths: ~ 0.3 nm – 0.3 pm • Frequencies: ~ 1018 Hz - 1021 Hz • Energy: ~ 4 keV – 4 MeV