4. The Electromagnetic Spectrum Flashcards
What is a the electromagnetic spectrum?
The range of signals encompassing all frequencies is referred to as the electromagnetic spectrum
How is a signal located on the spectrum?
According to its frequency and wavelength
What is frequency?
The number of cycles of a repetitive wave that occur in a given period of time
What is a cycle?
Two voltage polarity reversals, current reversals or EM field oscillations
How is frequency measured?
cycles per second (cps)
What is the unit of frequency?
hertz (Hz)
What is wavelength?
The distance occupied by one cycle of a wave and is usually expressed in meters. It is also the distance travelled by an EM wave during the time of one cycle.
It is represented by the Greek letter lambda - λ
How is wavelength calculated?
λ = c / f
c = speed of light (3*10⁸ m/s)
What is bandwidth?
The portion of the spectrum occupied by a signal
What is channel bandwidth?
It refers to the range of frequencies required to transmit the desired information
What are the three types of lightwaves?
Infrared; visible spectrum; ultraviolet
Where is infrared used?
In astronomy to detect stars etc; for guidance of weapons systems to detect heat from airplanes or missiles; TV remote-control units and in new wireless LANs and fibre-optic communication
What is the visible spectrum used for?
Usually for tremendous amounts of information
What is ultraviolet used for?
Not used for communication, primarily used as medical.
