The Electromagnetic Spectrum

1. The Electromagnetic Spectrum Rainbows plus a whole lot more

2. Wave vocabulary

3. Colors of the rainbow? Violet Blue Green Yellow Orange Red

4. Describing light… Longer wavelength   Higher frequency  Higher energy

5. Describing light… Wavelength (nm)

6. More than meets the eye… Electromagnetic Spectrum

7. Most waves require a medium. EM radiation does not. They can travel in a vacuum But what is electromagnetic radiation?

8. High to low energy • Gamma rays • X-rays • Ultraviolet • Visible • Infra-red • “below red” • Microwaves • Cell phones • Radio waves Ionizing radiation

9. Ionizing radiation • Subatomic particles or electromagnetic waves energetic enough to detach electrons from atoms or molecules, ionizing the atoms or molecules. GlossaryEntry I Gamma rays, X-rays, high energy ultraviolet light, alpha particles, and beta particles are examples of ionizing radiation.

10. Uses for the Electromagnetic Spectrum

11. Your body emits IR radiation

12. Try it Longer wavelength?   Higher frequency?   Higher energy? 

14. Energy of the rainbow Violet Indigo Green Yellow Orange Red 2.76 eV 2.51 eV 2.2 eV 2.1 eV 2.0 eV 1.65 eV

15. Try it ____ Ultraviolet ____ X-rays ____ Radio waves ____ Gamma rays ____ Visible ____ Infra-red ____ Microwaves • Rank in order of lowest to highest • Frequency • Wavelength • Energy

16. Calculating energy Energy = Planck’s constant times frequency E = h•ν h = 6.62 x 10-34Joules•second (J•s) = 4.13 x 10-15 electron Volt•second (eV•s) ν = frequency in Hertz (cycles/second) Also remember c = λ•ν c = speed of light = 3.00 x 108 m/s So E = h • c / λ

17. Try it!! • Calculate the energy of a photon of infra-red radiation with a wavelength of 800 nm. • Your cell phone emits energy in the microwave region. Calculate the energy of a photon of cell-phone radiation with an wavelength of 10 cm. • The energy of a photon is measured as 4x10-19 joules . In what region of the electromagnetic spectrum does it reside? (Hint: calculate  in nm)

18. wavelength • frequency • ionizing radiation • amplitude • photon Vocabulary Skills • Describe the electromagnetic spectrum using wavelength, frequency or energy • Rank energies of visible light • Rank energies of electromagnetic spectrum • Convert energy  wavelength, frequency  energy Concepts • EM radiation does not require a medium • Can travel in a vacuum • EM radiation travels in packets called photons • Higher energy EM radiation ionizes atoms or molecules Stuff to know