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Wavelength, Frequency & Energy

Wavelength, Frequency & Energy. **You’ll need a calculator**. White Light. Continuous spectrum of colors from the visible spectrum within the EMS ROYGBIV – red , orange , yellow , green , blue , indigo , violet. Electromagnetic Spectrum. Visible Wavelengths.

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Wavelength, Frequency & Energy

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  1. Wavelength, Frequency & Energy **You’ll need a calculator**

  2. White Light • Continuous spectrum of colors from the visible spectrum within the EMS • ROYGBIV – red, orange, yellow, green, blue, indigo, violet

  3. Electromagnetic Spectrum

  4. Visible Wavelengths SHORTEST WAVELENGTH HIGHEST FREQUENCY HIGHEST ENERGY LONGEST WAVELENGTH LOWEST FREQUENCY LOWEST ENERGY

  5. Wavelength (λ) • Distance from top to top (or bottom to bottom) of a wave • Measured in nanometers (nm) • Conversion: 10-9 m = 1 nm Wavelength (λ)

  6. Frequency (ν) • how frequent the waves pass a fixed point • Measured in cycles per second or Hertz • 1/s or s-1 or Hz • Conversion: 106 Hz = 1 MHz

  7. Energy (E) • Energy of a wave • Measured in Joules (J) or kiloJoules (kJ) • Named after James Prescott Joule • Conversion: 103 J = 1 kJ

  8. Speed of Light Equation c = λν Speed of light = wavelength x frequency Speed of light (c) is ALWAYS = 3.00 x 108 m/s Solving for λ: Solving for ν:

  9. Example: Find λ Sig fig Hint:b/c multiplying/dividingreport with fewest sig figs from all given values in problem ignore constants Into calculator: 3.00E8/5.00E6 then enter • What is the wavelength of a wave with a frequency of 5.00 x106 Hz? λ = ? c = 3.00 x 108 m/s ν = 5.00 x 106 Hz or 1/s

  10. Example: Find ν Sig fig Hint:b/c multiplying/dividingreport with fewest sig figs from all given values in problem ignore constants 1/s or Hz Into calculator: 3.00E8/3.33E-9 then enter • What is the frequency of a wave with a wavelength of 3.33 x 10-9 m? ν = ? c = 3.00 x 108 m/s λ = 3.33 x 10-9 m

  11. Planck’s Energy of a Photon Equation E = hν Energy = Planck’s constant x frequency Planck’s constant (h) is ALWAYS = 6.626 x 10-34 J·s

  12. Example: Finding E with ν Sig fig Hint:b/c multiplying/dividingreport with fewest sig figs from all given values in problem ignore constants = 1.067 x 108 Hz or 1/s J Into calculator: 6.626E-34*1.067E8 then enter • What is the energy of a radio wave with a frequency of 106.7 MHz? E = ? h = 6.626 x 10-34 J·s ν = 106.7 MHz

  13. Energy from the Wavelength and If frequency is notknown but wavelength is, you can substitute for frequency in the equation: Know So substitute for v and get:

  14. Example: Finding E with λ Sig fig Hint:b/c multiplying/dividingreport with fewest sig figs from all given values in problem ignore constants c = 3.00 x 108 m/s = 7 x 10-7 m J J Into calculator: 6.626E-34*3.00E8 then enter then /7.00E-7 • What is the energy of a wave with a wavelength of 700 nm? E = ? h = 6.626 x 10-34 J·s λ = 700 nm

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