Electromagnetic Waves

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Electromagnetic Waves
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About Electromagnetic Waves
Electromagnetic Waves waves that carry energy
without requiring a medium - produced by
changing electrical and magnetic fields -
behave as transverse waves - the electrical and
magnetic fields move perpendicular to the
direction of energy travel Because they require
NO MEDIUM, electromagnetic waves can pass through
space The energy carried by electromagnetic waves
is called electromagnetic radiation
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About Electric and Magnetic Fields
Electric and Magnetic fields are areas in space
where there either an electric or magnetic
force Whenever you have a changing magnetic field
you will have a changing electric field and vice
versa - when one field changes, so does the other
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The Speed of Electromagnetic Waves
The speed of all electromagnetic waves in a
vacuum (outer space) is equal to the speed of
light Speed of Light 300,000,000 m/s When
entering our atmosphere, or changing mediums,
electromagnetic waves slow down - even when
slowing down, electromagnetic waves travel a
million times faster than the speed of sound. We
can calculate the wavelength and frequency of all
electromagnetic waves using the same equations as
before - Because we are working with very large
and very small numbers we need to understand
scientific notation
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Scientific Notation

• Scientific notation is a shorthand used in
  science and math to write really large numbers in
  a shorter form using exponents.
• How It Works
• Place a decimal point after the first non-zero
  number in the large number
• Write out all the digits in between the first and
  last non-zero numbers in the large number
• Multiply by 10e, where e is the number of times
  you need to move the decimal to write the whole
  number
• -- if e is positive, you move the decimal to the
  right
• -- if e is negative, you move the decimal to the
  left

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Practice With Scientific Notation

• Write the following whole numbers in Scientific
  Notation
• 456,000 ?
• .007204000 ?
• .00000001 ?
• Write the following as whole numbers
• a) 5.15 x 108 ?
• b) 3.662 x 10 -4 ?
• c) 3.00 x 102 ?

4.56 x 105
7.204 x 10-3
1.0 x 10-8
515000000
.0003662
300
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Multiplying and Dividing In Scientific Notation
Multiplying and dividing in scientific notation
is very easy! Just split the equation into two
parts the decimal and the 10 to the
exponent. For Division Divide the top decimal by
the bottom decimal Subtract the bottom exponent
from the top exponent For Multiplication Multiply
the decimals together Add the exponents together
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Practice Multiplying and Dividing Using
Scientific Notation

• (3.33 x 107)
• (1.11 x 105)
• 2. (5.29 x 10-9) x (8.00 x 104)

3.00 x 102
4.232 x 10-4
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Using Scientific Notation to Calculate Wavelength
and Frequency
Remember that the speed of electromagnetic waves
is pretty much equal to the speed of light. We
use the letter c to represent the speed of
light. Therefore, our three wave equations are
now c ? x f ? c / f f c / ?
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Practice Problems
Practice Problem 1 What is the wavelength of an
electromagnetic wave with a frequency of 6.00 x
1016 Hz? Practice Problem 2 What is the
frequency of an electromagnetic wave with a
wavelength of 333 nm? (1 nm 1 x 10-9 m)
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The Electromagnetic Spectrum
Although all electromagnetic waves have the same
speed, they have different wavelengths and
frequencies. Electromagnetic waves with the
longest wavelengths have the smallest
frequencies. Electromagnetic waves with the
largest frequencies have the shortest
wavelengths. We classify electromagnetic waves on
a spectrum, from longest wavelength (smallest
frequency) to shortest wavelength (highest
frequency)
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Electromagnetic Spectrum Diagram
Increasing Frequency
Increasing Wavelength
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List of Electromagnetic Waves
Most Energetic Highest Frequency Gamma
Rays Shortest Wavelength X-Rays
Ultraviolet Rays Visible Light
Infrared Rays Microwaves Lowest
Frequency Radio waves Longest
Wavelength Least Energetic
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Uses of Electromagnetic Waves
Radio Waves -- longest wavelength, lowest
frequency -- used to transmit radio
signals Microwaves -- actually a type of
high-frequency radio wave -- still has a very
low frequency, long wavelength -- used in
radar -- used in ovens -- when water molecules
in food absorb the energy from microwaves, they
heat up, cooking food
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Uses of EM Waves (Contd)
Infrared Rays -- just below red in the visible
spectrum -- often felt as heat Visible Light --
less than 1 of the EM spectrum is visible
light -- range from longest wavelengths (red) to
shortest wavelengths (violet) -- this is what
we see!
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Uses of EM Waves (Contd)
Ultraviolet Rays -- means beyond violet --
small doses are used to produce Vitamin D --
comes from the sun -- large doses can kill and
damage cells -- often used to sterilize
equipment in hospitals X-Rays -- can pass
through soft tissue -- used to see pictures of
bones inside body
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Uses of EM Waves (Contd)
Gamma Rays -- highest-energy electromagnetic
wave -- can penetrate most tissues -- creating
the Incredible Hulk -- highest frequency,
shortest wavelength -- often given out by
radioactive substances -- sometimes used in
medicine, but because they are so damaging, need
to be seriously controlled
The End of it All!