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November 18, 2013

November 18, 2013. Electromagnetic Radiation. Objectives. At the end of class, you will be able to: List the forms of electromagnetic radiation Find wavelength or frequency of electromagnetic radiation. Waves and Particles. Particles are solid matter

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November 18, 2013

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  1. November 18, 2013

  2. Electromagnetic Radiation

  3. Objectives • At the end of class, you will be able to: • List the forms of electromagnetic radiation • Find wavelength or frequency of electromagnetic radiation

  4. Waves and Particles • Particles are solid matter • Waves are movement in matter, like an ocean wave or a wave at a football game

  5. Electromagnetic Radiation • Energy that travels through space as a wave EXAMPLES: • Gamma rays • X-rays • Ultraviolet rays • Visible light • Infrared • Microwaves • Radiowaves Electromagnetic spectrum

  6. In a vacuum all electromagnetic radiation travels at the speed of light. • This speed is c = 3.0 × 108 m/s

  7. Wavelength • Symbol: λ (lambda) • Units: m (meter) • Distance between corresponding points on a wave

  8. Frequency • Symbol: ν (nu) • Units: s-1, Hz, 1/s • Number of waves that pass a point per second

  9. Each form of light has different wavelength and frequency, but they all have the SAME SPEED

  10. increases • As wavelength ______________, frequency _______________. • As wavelength ______________, frequency ________________. decreases decreases increases

  11. The big equation for EM radiation: c = λν

  12. PRACTICE: • 1. What is the wavelength of electromagnetic radiation with a frequency of 2.0 × 1015 Hz? Where is this in the electromagnetic spectrum? If it is visible light, what color is the light? • Use formula: c = λν • Identify known information: c = 3.0 x 108 m/s ν= 2.0 × 1015 Hz • Plug known information into formula: 3.0 x 108 m/s = λ(2.0 × 1015 Hz) • Solve for λ λ = (3.0 x 108 m/s)/(2.0 × 1015 Hz) λ = 1.5 × 10-7 m

  13. Ultraviolet light

  14. PRACTICE: • 2. What is the frequency of light with a wavelength of 4.5 × 10-7 m? Where is this in the electromagnetic spectrum? If it is visible light, what color is the light? • Use formula: c = λν • Identify known information: c = 3.0 x 108 m/s λ = 4.5 × 10-7 m • Plug known information into formula: 3.0 x 108 m/s = (4.5 × 10-7 m) ν • Solve for ν ν = (3.0 x 108 m/s)/(4.5 × 10-7 m) ν=6.67 × 1014 Hz

  15. Visible light – Blue Visible light – Blue

  16. PRACTICE: • 3. What is the wavelength of electromagnetic radiation with a frequency of 5.85 × 1018 Hz? Where is this in the electromagnetic spectrum? If it is visible light, what color is the light? • Use formula: c = λν • Identify known information: c= 3.0 x 108m/s v = 5.85 x 1018Hz • Plug known information into formula: 3.0 x 108 m/s = λ(5.85 x 1018 s-1) • Solve for ν ν= (3.0 x 108 m/s)/(5.85 x 1018 s-1) = ν = 5.13 x 10-11m

  17. Gamma Rays (or X-rays) – The wavelengths overlap sometimes

  18. PRACTICE: • 4. What is the frequency of light with a wavelength of 64 cm? Where is this in the electromagnetic spectrum? If it is visible light, what color is the light? • Hint: make sure all variables are in units of m! • 64 cm | 1m = 0.64 m 100 cm

  19. PRACTICE: • 4. What is the frequency of light with a wavelength of 0.64 m? Where is this in the electromagnetic spectrum? If it is visible light, what color is the light? • Use formula: c = λν • Identify known information: c= 3.0 x 108 m/s λ= 0.64 m • Plug known information into formula: 3.0 x 108 m/s = (0.64m) ν • Solve for ν ν= (3.0 x 108 m/s)/(0.64m) = ν = 4.69 x 108Hz

  20. Radio Waves

  21. Check: • What is wavelength? • What is the unit for wavelength? • What is frequency? • What is the unit for frequency? • How can you find one if you know the other?

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