GCSEScienceWJECScience (Double Award)PhysicsRevision NotesElectricity, Energy & WavesFeatures of WavesCommunication Satellites

Communication Satellites (WJEC GCSE Science (Double Award): Physics): Revision Note

Exam code: 3430

Written by: Caroline Carroll

Reviewed by: Lucy Kirkham

Updated on 2 July 2026

Communication Satellites

Many important methods of communication rely on long wavelength electromagnetic radiation, including:
- Bluetooth, terrestrial television signals & local radio stations (using radio waves)
- Signals from mobile phone masts, wireless internet & communication satellites (using microwaves)
- Optical fibres (using visible or infra-red waves)

Communication satellites orbit the Earth and can communicate with base stations on the Earth's surface to relay information around the Earth
There are two different types of communication satellites:
- Geostationary satellites
- Geosynchronous satellites

Different Types of Communication Satellites

Geostationary and geosynchronous satellites orbiitngs around the Earth

Geosynchronous Satellites

The orbital period of a geosynchronous satellite is 24 hours which is in sync with the orbit of the Earth
A geosynchronous satellite will be in the same position above Earth once every 24 hours
- It is therefore only in communication with a base station on the surface of Earth once every 24 hours

Geostationary Satellites

A geostationary satellite also has a geosynchronous orbit, i.e. it takes 24 hours to orbit the Earth
A geostationary satellite:
- Remains directly above the equator and orbits in the same direction as the Earth spins
- Therefore, it always orbits at the same point above the Earth’s surface
- Is in constant communication with its base station

A Geostationary Satellite in Orbit

Geostationary orbit satellite, downloadable AS & A Level Physics revision notes

Geostationary satellites orbit the Earth every 24 hours above a fixed position on the Earth's surface

Geostationary satellites are used for telecommunication and television broadcast
Base stations on Earth send the microwave signals to satellites which relay them back to the desired locations
A minimum of 3 satellites located around the Earth is required for global coverage
Signals can be transmitted across the globe by travelling between ground base stations via satellites

Using Geostationary Satellites to Transmit Information

1-5-geostationary-satellites-wjec-physics

Information can be transmitted across the Earth using three geostationary satellites

Worked Example

Three satellites are positioned in orbit around the Earth to communicate with base stations A, B, and C on the ground, as shown in the diagram. The distance from a base station to a satellite is 36 000 km.

Diagram not drawn to scale

It takes 0.48 s for a signal to travel from base station A to base station C. The diagram shows the path of a signal sent from base station A to a satellite.

a) Complete the diagram to show how the signal reaches base station C.

b) Show that the signal travels at the same speed as the speed of light, 3 $\times$ 10⁸ m/s.

Answer:

a) Complete the diagram to show how the signal reaches base station C.

The signal must be sent from the satellite to base station B, up to the other satellite above B and C, before travelling to base station C
The signal cannot travel from one satellite to another, it must travel to a base station first:

1-5-geostationary-satellite-worked-example-answergeostationary-satellite-worked-example-answer

b) Show that the signal travels at the same speed as the speed of light, 3 $\times$ 10⁸ m/s.

Step 1: List the known quantities:

Distance the signal travels from A to C = 4 $\times$ 36 000 = 144 000 km = 1.44 $\times$ 10⁸ m
Time taken for the signal to travel from A to C = 0.48 s

Step 2: Write out the equation relating speed, distance and time:

$speed = \frac{distance}{time}$

Step 3: Calculate the speed of the signal:

$speed = \frac{1.44 \times 10^{8}}{0.48} speed = 3 \times 10^{8} m / s$

Examiner Tips and Tricks

Be careful with terminology, both types of satellites have a geosynchronous orbit. This means they orbit every 24 hours. However, a geostationary satellite remains above a fixed point above the equator on the Earth's surface whereas a geosynchronous satellite will only be above the same position above Earth once every 24 hours.

This is why geostationary satellites can be used for constant communications but geosynchronous satellites are only in communication with a base station once every 24 hours.

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

I would just like to say a massive thank you for putting together such a brilliant, easy to use website.I really think using this site helped me secure my top gradesin science and maths. You really did save my exams! Thank you.

Beth
IGCSE Student

This website is soooo useful and I can’t ever thank you enough for organising questions by topic like this. Furthermore, the name of the website could not have been more appropriate as it literally did SAVE MY EXAMS!

Fathima
A Level Student

Incredible! SO worth my money, the revision notes have everything I need to know and are so easy to understand. I actually enjoy revising! It makes me feel a lot more confident for my GCSEs in a few months.

Kate
GCSE Student

Absolutely brilliant, both my girls used it for A levels and GCSE. It's saves on paper copies, also beneficial exam questions ranked from easy to hard. It's removed a lot of stress from the exams.

Sameera
Parent

Just to say that your resources are the best I have seen and I have been teaching chemistry at different levels for about 40 years

Mark
Chemistry Teacher

Excellent