ELECTROMAGNETIC SPECTRUM (PowerPoint) by liaoqinmei

VIEWS: 125 PAGES: 18

• Energy from the Sun travels as
  electromagnetic waves or EM waves.
• They are waves that transfers energy though
  a field.
• Do not require matter to transfer its energy—
  occurs in a vacuum.
  Ocean waves need water
  Sound waves need air.
         Parts of a Wave
1. Crest- High point of wave.
2. Trough- Low point of wave.
    Electromagnetic Waves
Described by their physical wave features
3. Amplitude- Height of wave from center line
   to crest or trough.
4. Wavelength- Distance b/w 2 crests or
5. Frequency- # of waves passing a point
   each second.
Diagram of a Wave
• Arranged according to their increasing
  frequency and decreasing wavelength.
• All electromagnetic waves travel at the
  same speed.
• Amt of energy carried by an
  electromagnetic wave increases with
Electromagnetic Spectrum
• Each wavelength of EM energy interacts with
  objects on Earth in a different way.
• Some are reflected and some are absorbed.
• Color results from a combination of both
• When light strikes a leaf, leaf absorbs red
  light and but reflects green light.
• Reflected green light enters your eye—so
  you see a green leaf.
• Each type of matter has its own signature,
  called a reflectance curve, that shows how
  it reflects and absorbs energy.
• A reflectance curve is a graph that shows
  how a type of matter reflects visible, infrared
  and other wavelengths of light.
• Upward curve on graph indicates more of the
  wavelength is reflected.
• Downward curve on graph shows more of
  the wavelength is absorbed.
         Radio Waves
• Lowest frequencies and longest wavelengths.
• TV broadcast- Sound portion carried by AM
  waves (amplitude modulation) while picture
  portion carried as FM waves (frequency
• MRI- magnetic resonance imaging. Does not
  harm cells.
• Radio telescopes
• Microwaves-highest frequency rw. Food
  Most common use is cell phones.
• Radar
           Infrared Rays
•   Cannot be seen
•   Can be felt as heat- light bulbs, stove, sun.
•   Warmer object= more infrared rays
•   Cool object= absorb energy from infrared
    waves and become hotter.
•   Infrared lamps keep food hot, relieve sore
    muscles, and dry paint and hair.
•   Infrared camaras
•   Thermograms
•   Study pieces of art
     Visible Spectrum
• The only electromagnetic waves you can see.
• ROY G BIV red, orange, yellow, green, blue,
  indigo and violet.
• Half of energy given off by sun is visible light.
• Essential for photosynthesis.
      Ultraviolet Rays
• Electromagnetic waves with frequencies just
  higher than visible light.
• Energy of UV rays can kill cells.
• Used to kill germs in hospitals
• Preserve food in processing plants.
• Can be seen by many insects.
• UV rays cause your skin cells to produce
  Vitamin D
• Tanning is body’s way of protecting itself from
  UV rays. Can cause damage to skin, eyes
  and immune system
• Energy of X-rays allows it to pass through
• Used to take pictures of bone because bone
  absorbs X-rays.
• Exposure of X-rays over a long period of time
  can cause defects in cells.
• Been detected deep in space-believed to be
  in exploding stars.
         Gamma Rays
• Highest frequencies and shortest
• Have highest energy in spectrum.
• Radioactive materials and nuclear reactions
  emit gamma rays.
• Can penetrate 3-m of concrete.
• Gamma camara-patient is injected with a fluid
  that emits gamma rays. Move the camara
  over the body to form an image.

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