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The Electromagnetic Spectrum

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The Electromagnetic Spectrum ... This is why astronauts on spacewalks use radios to communicate. Radio waves are a type of electromagnetic wave. – PowerPoint PPT presentation

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Title: The Electromagnetic Spectrum


1
The Electromagnetic Spectrum
  • The electromagnetic spectrum consists of the
    colors that we see in a rainbow - from reds and
    oranges, through blues and purples.

2
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.

3
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.

4
  • 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.

5
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.

6
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.

7
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).

8
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.

9
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.

10
  • 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.

11
  • 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.

12
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

13
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.

14
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.

15
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.

16
The Visible Spectrum
  • Red, Orange, Yellow, Green, Blue, Indigo, and
    Violet are the colors of the visible spectrum.
    ROY G BIV

17
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!!!

18
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.

19
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.

20
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

21
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