Radio waves Flashcards
+ uses
What are EM waves made up of?
oscillating electric and magnetic fields
How would you describe the ease of radio waves being transmitted through the air?
they’re transmitted easily through the air
Do radio waves cause damage if absorbed by the human body?
NO
How can you change the direction of a radio wave?
By reflecting it.
Why are they ideal for communication?
they don’t cause damage if absorbed by the human body and can be reflected to change their direction.
What can radio waves be produced by?
by oscillating charges
What do these oscillating charges produce?
oscillating electric and magnetic fields - which is what electromagnetic radiation is made of
How can we make oscillating charges?
using an alternating current
What is the frequency of the waves produced equal to?
the frequency of the alternating current
You can produce radio waves using an alternating current in an electrical circuit. What is the object in which charges (electrons) oscillate to create the radio waves called?
a transmitter
What happens when transmitted radio waves reach a receiver?
the radio waves are absorbed
Where is the energy transferred by the waves transferred to?
It’s transferred to the electrons in the material of the receiver.
This energy causes the electrons to oscillate and…
if the receiver is part of a complete electrical circuit it generates an alternating current which has the same frequency as the radio waves that generated it.
How long are the wavelengths of radio waves?
> 10cm
What are the wavelengths of long-wave radio waves?
1-10km
What do long-wave radio waves diffract around?
Hills, tunnels and the curved surface of the earth.
Why can long-wave radio waves be used for long range communications?
they can transmit signals to a receiver that is not in the line of sight of the transmitter
What are the wavelengths of short-wave radio waves?
10-100m
What do short-wave radio waves reflect off of?
they reflect off the ionosphere (an electrically charged layer of gas in the upper atmosphere)
What does this reflection of short-wave radio waves allow?
communication with transmitters or receivers that are not in the line of sight.
What kind of signals do Bluetooth communication devices utilise?
Bluetooth communication devices also use short-wave signals to transfer radio waves over short distances.
What kind of waves do radio waves used to transmit signals for TV and radio use?
They use very short wavelengths. These waves do not diffract around large objects or reflect off the ionosphere and so the transmitter and receiver need to be in the line of sight of one another.
