The Electromagnetic Spectrum

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The Electromagnetic Spectrum

• The electromagnetic spectrum consists of the
  colors that we see in a rainbow - from reds and
  oranges, through blues and purples.

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What is the electromagnetic spectrum?

• The visible spectrum is just one small part of
  the electromagnetic spectrum. These
  electromagnetic waves are made up of two parts.
  The first part is an electric field. The second
  part is a magnetic field. So that is why they are
  called electromagnetic waves.

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What are waves?

• Have you ever ridden a wave in the ocean?
• Ocean waves travel on the surface of the water.
  You can see them and you can feel them. As you
  swim through the water, you can even make your
  own waves.

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• Have you ever seen a flag on a windy day?
• The wind creates waves in the flag. Both the
  waves in the flag and the ocean waves are waves
  that you can see. There are other kinds of waves.
  We cannot see these waves, but we experience them
  every day. These waves are called electromagnetic
  waves.

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Sound Waves?

• Sound is also a type of wave that we cannot see.
• Like ocean waves, sound waves need a medium to
  travel through. Sound can travel through air
  because air is made of molecules.
• These molecules carry the sound waves by bumping
  into each other, like Dominoes knocking each
  other over. Sound can travel through anything
  made of molecules - even water! There is no sound
  in space because there are no molecules there to
  transmit the sound waves.

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Whats the difference between sound waves and the
electromagnetic waves?

• Electromagnetic waves are unlike sound waves
  because they do not need molecules to travel.
• This means that electromagnetic waves can travel
  through air and solid materials - but they can
  also travel through empty space.
• This is why astronauts on spacewalks use radios
  to communicate. Radio waves are a type of
  electromagnetic wave.

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What are electromagnetic waves?

• Electromagnetic waves are formed when an electric
  field (which is shown in blue arrows) couples
  with a magnetic field (which is shown in red
  arrows).

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Electromagnetic Waves have different wavelengths.

• When you listen to the radio, watch TV, or cook
  dinner in a microwave oven, you are using
  electromagnetic waves.

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Waves!!

• Radio waves, television waves, and microwaves are
  all types of electromagnetic waves. They only
  differ from each other in wavelength. Wavelength
  is the distance between one wave crest to the
  next.

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• Waves in the electromagnetic spectrum vary in
  size from very long radio waves the size of
  buildings, to very short gamma-rays smaller than
  the size of the nucleus of an atom.

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• What does "frequency" mean?
• The frequency of a wave is the number of waves
  per second

• What does "wavelength" mean?
• The wavelength is the distance from the peak of
  one wave to the next one.

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Wavelengths

• High frequency, Short wavelength
• Low frequency, Long wavelength
• Shortest Waves to Longest
• Gamma Rays
• X-Rays
• Ultra-Violet
• Visible Light
• Infra-Red
• Microwave
• Radio Waves

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Gamma Rays

• Shortest wavelength.
• These are nasty ones. They have very high energy
  and will even go through metals.
• Gamma rays and X-Rays can cause cancer, but gamma
  rays can also be used to destroy cancer cells
  this is radio-therapy.

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X-Rays

• X-Rays have so much energy and such a short
  wavelength that they can go right through you.
• However, they cannot get through bone as easily
  as they can get through muscle.
• This is because your bones contain so much
  Calcium.

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Ultra Violet

• These waves have very high energy and very short
  wave lengths shorter than visible light.
• Some animals like honey bees can see ultra-violet
  light.
• Some plants have white flowers, at least you
  think that they are all white, but they may
  appear to be different colors to a honey bee
  because of the amounts of ultra-violet light
  which they reflect.

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The Visible Spectrum

• Red, Orange, Yellow, Green, Blue, Indigo, and
  Violet are the colors of the visible spectrum.
  ROY G BIV

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Infra Red

• These radio/light waves have a very short
  wavelength their wavelength is longer than
  visible light.
• Infra-red can be detected by special infra-red
  film.
• Animals like the pit-viper have infra-red
  detectors so that they can find their prey in the
  dark.
• You have been warned!!!

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Microwaves

• Microwaves have such a short wavelength that they
  are very easily absorbed by water.
• This is why they are used in microwave ovens.
• What happens is that when the water in your TV
  dinner absorbs the microwaves, the energy of the
  microwaves is converted into heat it makes the
  water molecules vibrate faster. Thus cooking your
  food.

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Radio Waves

• Radio waves have a much longer wavelength that
  light waves. The longest waves are several
  kilometers in length. The shortest ones are only
  millimeters long.
• I like these waves they are used for radio
  broadcasts, amateur radio, television, and mobile
  phones.
• Different parts of the radio spectrum have been
  allocated to the various services.

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Type of Radio Waves

• Long Wave, around 12 km in wavelength. The radio
  station "Atlantic 252" broadcasts here.
• Medium Wave, around 100m in wavelength, used by
  BBC Radio 5 and other "AM" stations.
• VHF, which stands for "Very High Frequency" and
  has wavelengths of around 2m. This is where you
  find stereo "FM" radio stations, such as "Galaxy
  101" and "GWR FM". Further up the VHF band are
  civilian aircraft and taxis.
• UHF stands for "Ultra High Frequency", and has
  wavelengths of less than a meter. It's used for
  Police radio communications, military aircraft
  radios and television transmissions

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