Electromagnetic spectrum

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Electromagnetic spectrum

  1. 1. Electromagnetic Spectrum<br />NATURE OF LIGHT<br />
  2. 2. Electromagnetic Spectrum<br />The electromagnetic spectrum comprise of the following:<br />1. Radio waves<br />Electromagnetic radiation with wavelengths that range from hundreds of meters to less than a centimeter.<br />Familiar due to their use in communications.<br />AM Radio band – 540 to 1, 650 kHz.<br />FM band – 88 – 108 MHz<br />Also includes shortwave radio transmissions and television signals. <br />
  3. 3. Electromagnetic Spectrum<br />2. Microwaves <br />Electromagnetic that range from approximately 1 ft (30 cm) in length to the thickness of a paper.<br />Microwave oven heat food by causing water molecule to rotate at a frequency of 2.45 GHz.<br />In astronomy radiation of a wavelength of 8.2 inch (21 cm) has been used to map neutral hydrogen (H) throughout the galaxy.<br />RADAR is also included in this region.<br />
  4. 4. Electromagnetic Spectrum<br />3. Infrared<br />Electromagnetic radiation that comprises the region of the electromagnetic spectrum where the wavelength of light is measured from 1 mm to 400 nanometer.<br />Discernible to humans as heat.<br />Discovered by W. Herschel by dispersing sunlight through a prism and measuring the temperature increase just beyond the red end of the spectrum.<br />
  5. 5. Electromagnetic Spectrum<br />4. Visible light<br />Electromagnetic radiation in the range visible to the human eye between approximately 4, 000 and 7, 700 angstroms.<br />Wavelengths to which the human eye is sensitive.<br />Easily pass Earth’s atmosphere.<br />Further broken down into the familiar color of a rainbow. (MR. ROY G. BIV) <br />
  6. 6. Electromagnetic Spectrum<br />5. Ultraviolet<br />Electromagnetic radiation ranging in wavelength from 400 to 10 billionth of a meter.<br />Has many important effects on Earth.<br />The ozone absorbs much of the UV radiation from the sun.<br />UV that reaches the Earth’s surface can cause suntans and sunburns. <br />
  7. 7. Electromagnetic Spectrum<br />6. X-rays<br />Electromagnetic radiation that are highly energetic with wavelengths ranging from about 10 billionths of a meter to 10 trillionths of a meter.<br />Useful in medical and industrial radiography.<br />Can pass through the body.<br />Allows doctors to study bones and teeth.<br />Do not pass Earth’s atmosphere so astronomers must place X-ray telescopes in space. <br />
  8. 8. Electromagnetic Spectrum<br />7. Gamma rays<br />Electromagnetic radiation that are most energetic and are comprised of light with wavelengths of less than about ten trillionths of a meter and include waves with wavelengths smaller than the radius of an atomic nucleus (1015m).<br />Produced by nuclear processes during radioactive decay or in nuclear reactions in space.<br />
  9. 9. Spectroscopy<br />The study of the spectra especially to determine the chemical composition of substances and the physical properties of molecules, ions and atoms.<br />Study of the properties of light that depend on wavelength.<br />Newton’s use of prism dispersing the visible light into the rainbow of colors initiated the study of spectroscopy. <br />
  10. 10. Spectroscopy<br />Spectroscope<br />The instrument for studying spectra; an instrument for dispersing light, usually light in the visible range, into a spectrum in order to measure it.<br />
  11. 11. Types of Spectrum<br />1. Continuous Spectrum<br />2. Dark-line Spectrum<br />3. Bright-line Spectrum <br />
  12. 12. Types of Spectrum<br />1. Continuous spectrum<br />Is produced by an incandescent solid, liquid or gas under high pressure.<br />Consists of an unfiltered band of color.<br />E.g. Common light bulb<br />
  13. 13. Types of Spectrum<br />2. Dark-line spectrum (Absorption spectrum) <br />Is produced when “white” light is passed through the a comparatively cool gas under low pressure.<br />Gas absorbs selected wavelengths of light, so the spectrum that is produced appears as a continuous spectrum but with a series of darklines.<br />
  14. 14. Types of Spectrum<br />3. Bright-line spectrum (emission spectrum)<br />Is produced by a hot (incandescent) gas under low pressure.<br />It is a series of bright lines of particular wavelengths depending on the gas that produces them.<br />These bright lines appear in the exact location as the dark lines that are produced by this gas in a dark-line spectrum (absorption). <br />
  15. 15. Spectrum<br />
  16. 16. Spectrum<br />The spectrum coming from the sun contains thousands of dark lines.<br />Over 60 elements have been identified by matching those lines with those elements known on Earth.<br />
  17. 17. Spectrum<br />TWO FACTORS CONCERNING A RADIATING BODY IS IMPORTANT <br />1. If the temperature of a radiating surface is directly proportional to the fourth power of its absolute temperature.<br />Stefan Boltzman Law<br />The energy radiated by a body is directly proportional to the fourth power of its absolute temperature.<br />Eg. Star – 2 times brighter – energy emitted will be 2 raise 4, it means the star released 16 times more energy.<br />
  18. 18. TWO FACTORS CONCERNING A RADIATING BODY<br />2. As the temperature of an object increases, a larger proportion of its energy is radiated at shorter wavelengths.<br />E.g. <br />Heated metal rod <br />Hot - Red color – longer wavelength<br />Hotter – Blue color – shorter wavelength<br />Red stars – hot<br />Blue stars - hotter <br />
  19. 19. Sodium lines<br />
  20. 20. End of presentation<br />

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