Physics 0625 · syllabus 3.3
Cambridge IGCSE Physics 0625 — Electromagnetic spectrum topical past papers
The order of the electromagnetic spectrum, the speed all its waves share, typical uses and dangers, communication with satellites, and analogue and digital signals.
- Questions
- 935
- Years
- 2009–2026
- With mark scheme
- 99%
- Questions 2022–2026
- 383
Anyone can browse these pages. Opening the questions and their mark schemes takes a free Momentum account.
What Electromagnetic spectrum covers
Electromagnetic waves form one continuous spectrum. In order of increasing frequency, which is decreasing wavelength, the main regions are radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. All of them are transverse and all travel at the same speed in a vacuum; Extended candidates know that speed is 3.0 × 10⁸ m/s and almost the same in air.
Each region has its uses. Radio waves carry radio and television broadcasts, reveal objects in astronomy and read RFID tags; microwaves cook food and carry mobile-phone and satellite-television signals; infrared is used in grills, television remote controls, intruder alarms, thermal-imaging cameras and optical fibres; visible light lets us see and take photographs; ultraviolet makes security ink glow, so it is used to mark property and check bank notes, and it kills microbes in drinking water; X-rays image bones and scan luggage; gamma rays sterilise food and medical equipment and are used to detect and treat cancer. Too much exposure does harm: microwaves heat body tissue from inside, infrared burns the skin, ultraviolet damages skin cells and eyes and can cause skin cancer, and X-rays and gamma rays can mutate or kill cells.
Signals reach artificial satellites mainly as microwaves. Satellite television and some satellite phones use geostationary satellites, while other satellite phones use satellites in low orbits. Extended candidates explain why mobile phones and wireless internet use microwaves, which pass through some walls and need only short aerials; why Bluetooth uses radio waves, which pass through walls but are weakened; and why optical fibres carrying visible light or infrared give cable television and fast broadband. They also contrast analogue signals, which vary continuously, with digital ones, which take only two values, and explain why digital signals carry data faster and keep their quality over long distances: they can be regenerated accurately, with the noise removed.
In the syllabus
The headings this topic has in the Cambridge International 2026–2028 syllabus, as the board prints them.
- 3.3 Electromagnetic spectrum
What you should be able to do
- Put the regions of the electromagnetic spectrum in order, by frequency and by wavelength
- Give typical uses of each region and the harm that too much exposure can do
- Use v = fλ with the speed of electromagnetic waves, 3.0 × 10⁸ m/s (Extended)
- State which waves are used to communicate with satellites, and which kinds of satellite carry phone calls and television
- Explain the choice of microwaves, radio waves or light for mobile phones, Bluetooth and optical fibres (Extended)
- Distinguish analogue from digital signals and explain the advantages of digital transmission (Extended)
Key ideas
- Increasing frequency, decreasing wavelength: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma
- All electromagnetic waves are transverse and travel at the same speed in a vacuum, 3.0 × 10⁸ m/s (the value for Extended)
- v = fλ, so at the same speed a higher frequency means a shorter wavelength
- Analogue signals vary continuously; digital signals have only two values, such as on and off
- Digital signals can be regenerated without their noise, so they travel further and carry data faster (Extended)
How Electromagnetic spectrum has been examined
From 2022 to 2026, Electromagnetic spectrum was on Paper 4 · Theory (Extended) in 14 of 14 exam series, worth about 12% of that paper’s marks.
| Paper | Questions | Share of marks | Series |
|---|---|---|---|
| Paper 1 · Multiple Choice (Core) | 136 | 11% | 14 of 14 |
| Paper 2 · Multiple Choice (Extended) | 142 | 11% | 14 of 14 |
| Paper 3 · Theory (Core) | 42 | 11% | 14 of 14 |
| Paper 4 · Theory (Extended) | 38 | 12% | 14 of 14 |
| Paper 6 · Alternative to Practical | 25 | 21% | 12 of 14 |
Momentum’s own count, over the questions in its bank for these years: a series is one exam session, every zone included, and a question filed under two chapters counts in both. Median marks per question: 1. The bank files this topic together with neighbouring ones, so these figures count every question in its chapters, including some on those topics.
Filed in Momentum under: Rays and Waves.
A worked example
A Wi-Fi router transmits microwaves of frequency 5.0 GHz, and a radio station broadcasts at 98 MHz. Find both wavelengths, and say which wave travels faster through the air.
- Microwaves: f = 5.0 × 10⁹ Hz, so λ = v/f = (3.0 × 10⁸) / (5.0 × 10⁹) = 0.060 m
- Radio: f = 98 × 10⁶ Hz = 9.8 × 10⁷ Hz, so λ = (3.0 × 10⁸) / (9.8 × 10⁷) = 3.1 m
- Both are electromagnetic waves, so both travel at about 3.0 × 10⁸ m/s in air
- Check: the higher frequency, the microwave's, goes with the shorter wavelength, as v = fλ requires
Answer: 6.0 cm for the microwaves and 3.1 m for the radio waves; neither travels faster
Written by Momentum for this page, with its own numbers; it is not taken from a past paper.
Mistakes that cost marks
- Saying higher-frequency waves travel faster — all electromagnetic waves have the same speed in a vacuum; a higher frequency means a shorter wavelength
- Putting ultraviolet and infrared, or X-rays and gamma rays, in the wrong order — infrared lies between microwaves and visible light, ultraviolet lies beyond violet, and gamma rays have the highest frequency
- Naming cell mutation as the danger of microwaves or infrared — microwaves heat tissue and infrared burns skin; mutation and cancer come from ultraviolet, X-rays and gamma rays
- Saying digital signals are better because they 'have no noise' — they pick up noise like any signal, but with only two values they can be cleaned up and regenerated accurately
- Dropping the powers of ten in v = fλ — a 100 MHz radio wave has λ = (3.0 × 10⁸) ÷ (1.0 × 10⁸) = 3.0 m
Exam technique
- Learn one use and one danger for each region, and name the region exactly as it appears in the spectrum
- When asked why a region suits a job, give the property that matters, such as passing through walls or needing only a short aerial
- Write frequencies in hertz in standard form before calculating: MHz means × 10⁶ and GHz means × 10⁹
Practising in Momentum
- Every question in a chapter as one list, from every paper and year in the bank, newest first or shuffled.
- Each question turns over to its own part of the mark scheme, where the board published one.
- Narrow by paper, year, session, zone and marks, and star the questions worth keeping.
- Pick chapters, a number of questions and a time, and the exam builder draws a mock to sit and mark.
Past-paper questions and mark schemes are the copyright of Cambridge International. Momentum shows them to signed-in learners for revision and does not publish them on these pages.