Explain wireless and optical-fibre communication choices
Connect mobile phones, wireless internet, Bluetooth, cable television and broadband to their listed carriers and transmission properties.
Section P3.3 · Electromagnetic spectrum
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Locate radio, microwaves, infrared and visible regions.
- Explain a carrier and optical-fibre guidance.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What happens to a Bluetooth signal when it passes through a wall?
What you will learn
- Explain the specified wireless carrier choices and wall effects.
- Explain suitable visible/infrared fibre bands and high-data-rate uses.
Describe wireless links with their limits
Mobile phones and wireless internet use microwaves in the syllabus description. Suitable microwave signals can penetrate some walls and need only short transmitting and receiving aerials. 'Some' matters: material, thickness and frequency affect transmission, and a wall can weaken a link.
Bluetooth uses radio waves. Radio can pass through walls, but the signal is weakened on doing so. Bluetooth's common microwave-frequency band is also part of the wider radio range; the two labels are not contradictory. These properties explain useful short-range links, not guaranteed reception behind every obstacle.
Guide selected light through a cable
Optical fibres carry suitable visible light or infrared for cable television and high-speed broadband. Glass transmits visible light and some infrared wavelengths, and short-wavelength infrared or visible signals can support high data rates. The data are represented by controlled signals travelling along the guided path.
High carrier frequency is not identical to the data rate. Encoding, bandwidth, detectors and the link also matter. Do not divide an optical carrier frequency by two and claim that as a universal broadband rate. Real fibres have losses and selected transmission bands.
Sources for this lesson
Pause and explain
Why are suitable light signals useful in optical-fibre broadband?
Worked example
Explain a wireless internet link, Bluetooth through a wall and a broadband fibre cable.
Show the worked solution
- Wireless internet uses microwaves with suitable wall transmission and short aerials.
- Bluetooth uses radio signals weakened by the wall.
- A fibre guides suitable visible/infrared signals supporting high data rates.
Answer Microwave wireless; attenuated Bluetooth radio; guided visible/infrared fibre communication.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Give two listed reasons microwaves suit mobile-phone and wireless internet links.
Give me a hint
Recall both the barrier property and aerial size.
Compare my reasoning
- Suitable signals can penetrate some walls.
- Only a short aerial is required.
- These support practical transmission and reception.
Some-wall penetration and short aerials.
Look for these in your work
- Include both properties.
- Retain the word some.
Describe Bluetooth's carrier and the effect of a wall.
Give me a hint
Use the syllabus's broad radio label with its attenuation limit.
Compare my reasoning
- Bluetooth uses radio waves.
- They can pass through walls.
- The signal is weakened on passing through.
Radio waves; wall transmission with weakening.
Look for these in your work
- Name the carrier.
- State the weakening.
A fibre carries an optical carrier at 2.0 × 10¹⁴ Hz. Does this establish its exact data rate?
Give me a hint
Separate wave oscillations from encoded information symbols.
Compare my reasoning
- The number is carrier frequency.
- Data rate depends on encoding and the usable link.
- No exact data rate follows from that frequency alone.
No; the carrier frequency alone does not determine the data rate.
Look for these in your work
- Name both quantities.
- Retain fibre transmission and system limits.
Common mistakes
- Not every wall transmits every signal.
- Microwaves are within the broader radio-frequency range.
- Carrier frequency is not automatically data rate.
What can you explain now?
Does glass transmit every infrared wavelength equally well?
Compare with the explanation
No.
The listed fibre use relies on suitable visible or infrared transmission bands.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain the listed wireless and fibre choices with wall weakening, selected bands and data-rate limits.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.