Waves

YOU ARE LEARNING:

Radiowaves

Radio waves have the longest wavelength out of the EM spectrum. They are used in communications.

Out of these electromagnetic waves, which has the longest wavelength?

So radio waves have the longest wavelength out of the EM spectrum. Does this mean they have the lowest or the highest frequency in the EM spectrum?

What energy do radio waves have in relation to the rest of the EM spectrum?

What do you think radio waves might be used for?

Can humans hear radio waves?

We can generate EM waves, like radio waves, with an alternating current (AC). This is made up of oscillating charges which will produce the oscillating electric and magnetic fields that make up an EM wave.

We use a transmitter to create an alternating current (AC) which generates radio waves.

We use an oscilloscope to see the frequency of the current, which tells us the frequency of the wave.

We use a receiver to absorb the radio waves to create an AC. Will this frequency be the same as the frequency of the initial current of the transmitter? Answer yer or no.

So we can use a transmitter and receiver to send radio waves using and transfer information.

This extremely useful for telecommunication.

Now, imagine you want to send radio waves to communicate from England to China. How do you think the radio waves travel?

Long radio waves are used for communicating across huge distances, like from England to China.

These diffract (bend) around the Earth.

Short radio waves are used for communicating across large distances as well as short distances, like for bluetooth.

For long distances, short radio waves get reflected between the ionosphere (a layer of charged particles in the atmosphere) and the surface of the Earth.

In addition to long radio waves and short radio waves, we can also use very short radio waves.

Very short radio waves need to travel directly from the transmitter to the receiver.

These are used for things liker radios and terrestrial TVs (not satellite or cable TV).

What do you think causes bad reception when listening to the radio?

Mary is driving through a tunnel that goes through a mountain. Will she be able to receive any radio signal? Answer yes or no.

To sum up

Radio waves are electromagnetic waves with...

Radio waves are used in communications and are created by generating an AC which can be sent from a transmitter to a receiver.

Long radio waves are used for very long distances. Short radio waves are used for long distance as well as short distance. Very short radio waves are used for terrestrial TVs and radios.