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Published byCalvin Safe Modified over 2 years ago

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November 18, 2013

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Electromagnetic Radiation

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

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

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

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In a vacuum all electromagnetic radiation travels at the speed of light. This speed is c = 3.0 × 10 8 m/s

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

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

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

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

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The big equation for EM radiation: c = λν

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PRACTICE: 1. What is the wavelength of electromagnetic radiation with a frequency of 2.0 × 10 15 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 10 8 m/s ν = 2.0 × 10 15 Hz Plug known information into formula: 3.0 x 10 8 m/s = λ( 2.0 × 10 15 Hz) Solve for λ λ = (3.0 x 10 8 m/s)/ ( 2.0 × 10 15 Hz) λ = 1.5 × 10 -7 m

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Ultraviolet light

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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 10 8 m/s λ = 4.5 × 10 -7 m Plug known information into formula: 3.0 x 10 8 m/s = (4.5 × 10 -7 m) ν Solve for ν ν = (3.0 x 10 8 m/s)/ ( 4.5 × 10 -7 m) ν = 6.67 × 10 14 Hz

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Visible light – Blue

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PRACTICE: 3. What is the wavelength of electromagnetic radiation with a frequency of 5.85 × 10 18 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 10 8 m/sv = 5.85 x 10 18 Hz Plug known information into formula: 3.0 x 10 8 m/s = λ (5.85 x 10 18 s -1 ) Solve for ν ν = (3.0 x 10 8 m/s)/(5.85 x 10 18 s -1 ) = ν = 5.13 x 10 -11 m

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

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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

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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 10 8 m/s λ = 0.64 m Plug known information into formula: 3.0 x 10 8 m/s = (0.64m) ν Solve for ν ν = ( 3.0 x 10 8 m/s)/(0.64 m) = ν = 4.69 x 10 8 Hz

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Radio Waves

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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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