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Electromagnetic Spectrum and Solar Radiation

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Electromagnetic Spectrum and Solar Radiation

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    1. Unit 4B.1

    5. Remembering the EM Spectrum Long, low, red, radio Short, high, gamma, vi (violet)

    9. Electromagnetic Radiation Characteristics Frequency (?)- the number of waves that pass a given point at each second also known as the rate of oscillation the frequency of a wave is directly proportional to its energy High frequency radiation is high energy radiation

    10. Electromagnetic Radiation EM Radiation: radiation ranging from low energy radio waves to high energy X-rays and gamma rays; includes visible light http://hyperphysics.phy-astr.gsu.edu/hbase/ems1.html http://lectureonline.cl.msu.edu/~mmp/applist/Spectrum/s.htm

    11. What is electromagnetic radiation? Composed of photons Photons = bundles of energy, packets of energy Photons travel as waves, at the speed of light Photons do not require a medium to travel (they can move through a vacuum!) Speed of Light: (c) is equal to the product of wavelength and frequency c = ?? = 3.0 x 108 m/s

    12. Wave Calculation Formulas E = h? E: energy of em radiation (Joules) h: Planks constant, 6.626 x 10-34 Joules/Hz ? : frequency (Hz or 1/second) ? ? = c ? : wavelength (meters or centimeters) ? : frequency (Hz or 1/second) c = 3.0 x 108 m/s or 3.0 x 1010 cm/s

    16. Example Problem #1 Calculate the wavelength of the yellow light emitted by a sodium lamp if the frequency of the radiation is 5.10 X 1014 Hz (5.10 X 1014 s-1)

    17. Example Problem #2 The laser used in CD players uses light with a wavelength of 950 nm. What is the frequency of this light? (1m = 109nm)

    18. Velocity of a Wave Velocity = f ? Ex: Calculate the velocity of a wave if the frequency is 5Hz and the wavelength is 12m Note: Hz = waves/sec Answer = 60 m/s

    19. Solar Radiation Solar radiation spreads over a large portion of the electromagnetic spectrum 45% in infrared (IR) region 46% in the visible region 9% in the ultraviolet (UV) region

    20. Infrared Radiation (1mm- 750nm) heat radiation Electromagnetic radiation with frequencies slightly lower than red light Causes certain bonded atoms to vibrate more energetically which results in temperature increase Short wavelength is transmitted to the earth and is reflected within the atmosphere

    21. Conduction vs. Convection vs. Radiation Conduction: heat transfer through contact Ex: hand on stove Convection: heat transfer through convection currents- through fluids Ex: warm breeze, heat rises, cold air falls Radiation: heat transfer through electromagnetic waves Ex: car heating up from the suns rays, popping popcorn in microwave

    23. Visible Radiation (750nm- 400nm) Red- 650nm Orange- 590nm Yellow- 570nm Green- 510nm Blue- 475nm Indigo- 445nm Violet- 400nm

    24. Ultraviolet radiation (400nm- 10nm) 3 types of UV radiation: UV-A: the longest wavelength and lowest energy (longer than 320nm) UV-B: higher energy; causes sunburn, long term exposure linked to skin cancer (280-320nm) UV-C: highest energy UV radiation; used to sterilize materials because UV-C photons have enough energy to break covalent bonds (shorter than 280nm)

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