GCSEAQACombined Science HigherPhysics Higher

Radio Waves are electromagnetic waves with wavelengths longer than $\bold{10 \textbf{ cm}}$. They are used to transmit signals to radios, televisions and Bluetooth communication devices

Radio waves can be produced by oscillating charges. These oscillating charges produce oscillating electric and magnetic fields – this is what electromagnetic radiation is made of.

We can make oscillating charges using an alternating current (ac)

The frequency of the radio waves produced depends on the frequency of the alternating current

The diagram below shows the process of transmitting and detecting radio waves. The ac supply causes electrons in the transmitter to oscillate. These electrons produce radio waves which are transmitted over as distance. At the receiver, the radio waves cause electrons to oscillate. The electrons produce an ac current in the receiver.

GCSECombined Science HigherPhysics HigherAQA

In general, radio waves are electromagnetic waves with wavelength longer than $10 \text{ cm}$, however they can also be split into different types of radio waves according to their wavelengths. Each type of radio wave has different uses.

Long-wave radio waves have wavelengths between $\bold{1}$ and $\bold{10} \textbf{ km}$. These radio waves diffract around large objects such as hills, tunnels and the curved surface on the Earth. This means that long-wave radio waves can transmit signals to a receiver that is not in the line of sight of the transmitter and therefore they can be used for long-range communications

Short-wave radio waves have wavelengths between $\bold{10}$ and $\bold{100} \textbf{ m}$. These waves do not diffract around large objects however they reflect off the ionosphere (an electrically charged layer of gas in the upper atmosphere). This also allows communication with transmitters or receivers that are not in the line of sight. Bluetooth communication devices also use short-wave signals to transfer radio waves over short distances.

Radio waves used to transmit signals for TV and radio 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.

GCSECombined Science HigherPhysics HigherAQA

@mmerevise

The ac current causes electrons to oscillate.

This produces oscillating electrical and magnetic fields which is a radio wave.

Gold Standard Education

These oscillations create an alternating current

Gold Standard Education

The long-wave radio waves diffract around large objects such as the mountain.

Gold Standard Education

TV signals require the transmitter and receiver to be in the same line of sight because they do not diffract around large objects or reflect off the ionosphere

Hence, TV signals cannot be transmitted through the mountain in the diagram.