Electromagnetic Waves

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Electromagnetic Waves
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• Electromagnetic waves are transverse waves
  consisting of changing electric and magnetic
  fields.
• Energy travels in the form of waves.
• They can travel in a vacuum as well as through
  matter.
• Electromagnetic radiation-
• the transfer of energy by
• electromagnetic waves
• traveling through matter or
• across space.

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Light, like sound and heat, is a form of energy.
The visible light we see is part of the
electromagnetic spectrum.
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Things to know

• frequency how often a wave passes a point in a
  certain time interval
• wavelength- the distance from one crest to the
  next or one trough to the next

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The speed of light depends on the medium.
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• The speed of light in a vacuum is
• 3 X 108 meters per second (300,000,000 m/sec)

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The Electromagnetic Spectrum

• Electromagnetic Spectrum- the full range of
  frequencies of electromagnetic radiation.
• This spectrum includes visible light and
  invisible waves
• radio wave
• microwaves
• infrared light
• ultraviolet light
• X-rays
• gamma rays

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Wavelength and Frequency
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Wavelength and Frequency of Light
Because the wavelength of light is so small,
scientists measure it in nanometers. One
nanometer (nm) is one billionth of a meter
(0.000000001 m).
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The electromagnetic spectrum includes
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Radio Waves

• Has the longest wavelength and the lowest
  frequency.
• Uses Radio, TV, radar, microwaves
• Radar radio detection and ranging, a system that
  uses reflected radio waves to determine the
  velocity and location of objects

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Microwaves

• Microwaves are used in cooking and communication.
• Microwaves have wavelengths in the range of
  centimeters.

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Infrared Rays

• Wavelength smaller than radio.
• slightly longer than red visible light.
• felt as warmth
• Used as a source of heat/or to detect heat
  differences.
• Thermograms-
• color-coded pictures
• that show variations
• in temperature.

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Visible Light

• Each wavelength in the visible spectrum
  corresponds with a specific frequency and a
  specific color.
• Light enables people
• to see, keeps people
• safe and helps them
• to communicate.

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Ultraviolet Rays

• Shorter wavelength and higher frequency than
  violet light.
• Sunlight contains ultraviolet light.
• The invisible light that lies just beyond violet
  light falls into the ultraviolet (UV) portion of
  the spectrum.

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X-Rays

• Have very short wavelengths.
• Less than 108 m.
• Used in medicine, industry and transportation
  by making pictures of the inside of solid
  objects.

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Gamma Rays

• Shortest wavelength in the electromagnetic
  spectrum.
• wavelengths shorter than 1010 m.
• Have the highest frequency.
• Have the most energy.
• Over exposure can be
• deadly.
• Used in the medical field
• to kill cancer cells and make pictures of the
  brain, and in industrial situations as an
  inspection tool.