Radiowaves Flashcards
What are EM waves made of ?
oscillating electric and magnetic fields
How are alternating currents formed and what is the frequency of them ?
made up oscillating charges. As charges oscillate, they produce oscillating electric and magnetic fields.
Frequency of waves produced will be equal to frequency of the ac
How do you produce radio waves ?
by using alternating current in an electrical circuit, object in which electrons oscillate to create radio waves = transmitter.
When transmitted radio waves reach a receiver, radio waves are absorbed
Where is energy carried ? What does this energy cause ?
Energy carried by wave is transferred to electrons in material of receiver. This energy causes the electrons to oscillate and receiver is part of complete electrical circuit = it generates AC
This current has same frequency as radio waves that generated it.
What are radio waves
EM radiation with wavelengths longer than 10cm
3 forms of radio waves
- long wave radio
- short wave radio signals
- medium wave signals
Uses and properties of long wave radio
Can be transmitted long distances ( London to halfway round the world )
This is because long wave lengths diffract around the curved surface of the earth .
Can also diffract around hills and into tunnels, which makes it possible for signals to be received even if receiver is not in line of sight of transmitter
Uses and properties of short wave radio signals
can be received at long distances from transmitter, this is because they’re reflected from ionosphere ( electrical charged layer in earths upper atmosphere )
Bluetooth use short wave radio waves to send data over short distances between devices without wire.
Uses and properties of medium wave signals
reflect from ionosphere depending on atmospheric conditions and time of day
The radio waves for TV and FM transmissions have …
short wavelengths = must be in line of sight with transmitter for reception = signal doesn’t bend
