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Frequency is the number of seconds per wave and is
measured in Hertz ( Hz )
Wave Equation for Light
v = Speed ( velocity ) of the wave in cm / s or m / s
f = Frequency in Hertz ( Hz )
= wavelength in cm or m…read more

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Using light for communication
Centuries ago smoke signals and bonfires were used to
Communication became easier after electric light was
Samuel Morse invented the Morse code which is a system
of dots and dashes representing letters and numbers…read more

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The Morse code
Mirrors and signalling lamps have been used to send
messages using the Morse code
The code is a series of dots and dashes that represent
individual letters of the alphabet…read more

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Advantages and Disadvantages of communications
Method Advantages Disadvantages
Light Sends messages very Light easier to see in
( e.g.…read more

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L ight
A mplification by
S timulated
E mission of
R adiation
A laser is a very narrow, high energy, intense beam of
It is very intense because all the waves have the same
frequency and are in phase
Laser light
White light, from a bulb, is made up of many different
Each is of a different frequency and out of phase…read more

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The light from a laser is at one frequency and in phase
Laser light
The crest and troughs appear at the same time
White light
The crests and troughs do not appear at the same time
Compact disks
Lasers are used to read compact disks, by reflecting of a
series of pits, representing digital signal
The plastic compact disk ( CD ) is pressed with a series of
fine pits
The pits represent a digital musical signal
The signal is read by a laser…read more

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The music layer is coated with a fine film of metal that
follows the pits exactly
The shiny metal film reflects the lasers light
The metal layer is covered by another layer of fine plastic
The music is sandwiched between two layers of plastic
This stops dust and scratches from affecting the sound…read more


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