What is the electromagnetic spectrum in the context of Edexcel IGCSE Physics?

The electromagnetic spectrum is a range of all types of electromagnetic radiation, which are waves of electric and magnetic fields. In Edexcel IGCSE Physics, students learn that this spectrum includes, in order of increasing frequency and decreasing wavelength: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

How are the different types of electromagnetic waves used in everyday applications?

Each type of electromagnetic wave has unique properties and uses. For example, radio waves are used for broadcasting and communications, microwaves for cooking and satellite transmissions, infrared for remote controls and thermal imaging, visible light for seeing, ultraviolet for sterilizing medical equipment, X-rays for medical imaging, and gamma rays for cancer treatment. Understanding these applications is part of the Edexcel IGCSE Physics curriculum.

What are the dangers associated with electromagnetic waves, and how can they be mitigated?

Some electromagnetic waves can be harmful. For instance, excessive exposure to ultraviolet rays can cause skin cancer, while X-rays and gamma rays can damage cells and tissues. To mitigate these risks, protective measures such as sunscreen, lead aprons, and limiting exposure time are recommended. These safety aspects are important in the study of the electromagnetic spectrum in Edexcel IGCSE Physics.

Why is the electromagnetic spectrum important in the study of waves in Physics?

The electromagnetic spectrum is crucial in Physics because it encompasses all forms of electromagnetic radiation, which are fundamental to understanding wave behavior. It helps explain phenomena such as reflection, refraction, and diffraction, and is essential for technologies like telecommunications and medical imaging. This understanding is a key component of the Edexcel IGCSE Physics syllabus.

How do wavelength and frequency relate to each other in the electromagnetic spectrum?

In the electromagnetic spectrum, wavelength and frequency are inversely related. This means that as the wavelength of a wave increases, its frequency decreases, and vice versa. This relationship is described by the equation: speed of light = wavelength × frequency. Understanding this concept is vital for Edexcel IGCSE Physics students studying waves and the electromagnetic spectrum.

Why is "Reversing the order of frequency vs wavelength" a common mistake in The Electromagnetic Spectrum?

Why it happens: Forgetting that v = f with v fixed means f and are INVERSELY related. How to avoid it: Memorise one direction (say, increasing frequency: radio → gamma) and remember the OPPOSITE ordering applies to wavelength. Source: 4PH1 Examiner Reports 2022-2024

Why is "Quoting visible light colours in the wrong order" a common mistake in The Electromagnetic Spectrum?

Why it happens: Some textbooks list red → violet (decreasing wavelength), others violet → red. How to avoid it: By WAVELENGTH (longest first): red, orange, yellow, green, blue, indigo, violet ('Richard Of York...'). By FREQUENCY (lowest first): the SAME order — red → violet. Edexcel mark schemes accept either ordering as long as it's clearly labelled.

Why is "Saying UV is used for sterilisation (when spec 3.12 names gamma)" a common mistake in The Electromagnetic Spectrum?

Why it happens: Both UV and gamma kill bacteria. How to avoid it: Spec 3.12 explicit pairings: UV → fluorescent lamps + bank notes; GAMMA → sterilising. Use the spec example. Source: 4PH1 Examiner Reports 2022-2024

Why is "Vague answers about hazards ('it's dangerous')" a common mistake in The Electromagnetic Spectrum?

Why it happens: Not memorising the spec 3.13 pairings. How to avoid it: Memorise each pairing: microwave → internal tissue heating; IR → skin burns; UV → cell damage / cancer / blindness; gamma/X → mutation, cancer. Source: 4PH1 Examiner Reports 2022-2024

Why is "Saying EM waves all travel at $3 \times 10^{8}$ m/s in ALL materials" a common mistake in The Electromagnetic Spectrum?

Why it happens: The phrase 'all EM waves travel at c' gets quoted out of context. How to avoid it: Spec 3.10 says 'in vacuum'. EM waves SLOW DOWN in glass, water etc. — this is what causes refraction (spec 3.17).

WavesEdexcel IGCSE Physics (4PH1)

The Electromagnetic Spectrum

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The Electromagnetic Spectrum — Pearson Edexcel International GCSE Physics 4PH1 Study Notes (2026 onwards, Spec Issue 4)

Seven groups (radio, micro, IR, visible, UV, X-ray, gamma) of a single continuous spectrum. All travel at $c = 3 \times 10^{8}$ m/s in vacuum. Memorise the ordering, the visible-colour sub-order red → violet, the spec 3.12 uses and the spec 3.13 hazards / protective measures.

What you’ll learn

Mapped to the Cambridge IGCSE 4PH1 syllabus (2026 onwards).

3.10 — Know that light is part of a continuous electromagnetic spectrum which includes radio, microwave, infrared, visible, ultraviolet, X-ray and gamma rays, and that all these waves travel at the same speed in a vacuum.
3.11 — Know the order of the electromagnetic spectrum in terms of decreasing wavelength and increasing frequency, including the colours of the visible spectrum.
3.12 — Explain some uses of electromagnetic radiations, including: radio (broadcasting and communications); microwaves (cooking and satellite transmissions); infrared (heaters and night vision equipment); visible light (optical fibres and photography); ultraviolet (fluorescent lamps); X-rays (observing the internal structure of objects, airport security and medical X-rays); gamma rays (sterilising food and medical equipment).
3.13 — Understand the detrimental effects of excessive exposure of the human body to electromagnetic waves, including microwaves (internal heating of body tissue), infrared (skin burns), ultraviolet (damage to surface cells and blindness), gamma rays (cancer/mutation), and describe simple protective measures against the risks.

The continuous EM spectrum (spec 3.10)

One spectrum, seven named groups.

The electromagnetic spectrum is a SINGLE CONTINUOUS RANGE of transverse waves. We divide it into named groups by approximate wavelength purely for convenience.

Group	Approx wavelength	Approx frequency
Radio	> 0.1 m	< 3 GHz
Microwaves	1 mm – 10 cm	3–300 GHz
Infrared (IR)	700 nm – 1 mm	0.3 – 400 THz
Visible light	400 – 700 nm	430 – 750 THz
Ultraviolet (UV)	10 – 400 nm	$10^{15}$ Hz region
X-rays	0.01 – 10 nm	$10^{17}$ Hz region
Gamma rays	< 0.01 nm	> $10^{19}$ Hz

Key properties shared by ALL EM waves (spec 3.10).

They are TRANSVERSE.
They travel at $c = 3 \times 10^{8}\,\text{m/s}$ in vacuum (spec 3.10).
They obey $v = f\lambda$ (spec 3.5).
They can be reflected and refracted (spec 3.9).
They DO NOT require a medium to travel (unlike sound).

In a material medium (glass, water, air), EM waves travel SLOWER than $c$ . The slowdown causes refraction. Numerical exam questions almost always set $v = c$ unless told otherwise.

One continuous spectrum, seven named groups.
All EM waves are transverse.
Speed = $3 \times 10^{8}$ m/s in vacuum.
Slower in glass/water → causes refraction.

Ordering the spectrum (spec 3.11)

Radio → gamma by frequency.

Decreasing wavelength / increasing frequency (spec 3.11):

$\text{radio} \to \text{microwaves} \to \text{infrared} \to \text{visible} \to \text{ultraviolet} \to \text{X-ray} \to \text{gamma}$

Use any memorable mnemonic, e.g. "Roman Men Invented Very Unusual X-ray Guns".

Visible-light sub-order. Inside visible, again in order of DECREASING wavelength (= increasing frequency):

$\text{red} \to \text{orange} \to \text{yellow} \to \text{green} \to \text{blue} \to \text{indigo} \to \text{violet}$

Standard mnemonic: "Richard Of York Gave Battle In Vain".

Quantitative reminder. A wave with wavelength 600 nm (orange light) has frequency

$f = \dfrac{c}{\lambda} = \dfrac{3 \times 10^{8}}{6 \times 10^{-7}} = 5 \times 10^{14}\,\text{Hz}$

Compare radio at $f \sim 10^{6}$ Hz and gamma at $f \sim 10^{20}$ Hz — fourteen orders of magnitude span.

Memorise: radio → micro → IR → visible → UV → X-ray → gamma.
Visible by wavelength: red, orange, yellow, green, blue, indigo, violet.
Frequency rises and wavelength falls in the SAME direction along the spectrum.

See the full worked example for the electromagnetic spectrum →

Uses of each band (spec 3.12)

Memorise the spec-named examples.

Edexcel awards a mark per correct pairing. The spec 3.12 list:

Radio waves — broadcasting (radio, TV) and communications. They diffract around hills and through buildings; long wavelength = robust signal.
Microwaves — cooking food (~2.45 GHz absorbed by water molecules); satellite TV and phone communications (penetrate the atmosphere).
Infrared (IR) — electric heaters, grills (cooking by IR radiation); night-vision equipment (warm objects glow in IR); short-range remote controls.
Visible light — optical fibres (light pulses carry digital data); photography (cameras capture reflected visible light).
Ultraviolet (UV) — fluorescent lamps (UV excites a phosphor coating which then emits visible light); detecting forged bank notes (security marks fluoresce in UV).
X-rays — observing the internal structure of objects (bones in medical imaging; weld inspection in industry); airport security (luggage scanning).
Gamma rays — sterilising food and medical equipment (gamma kills bacteria and viruses); radiotherapy (treating cancer tumours).

Why each band suits its use. A pattern question on Paper 1 may ask you to JUSTIFY the choice:

Radio: long wavelength → diffracts around obstacles → broadcast range.
Microwave: ~2.45 GHz resonates with water → heats food efficiently.
IR: absorbed by surfaces → surface heating; emitted by all warm objects → detected by thermal cameras.
UV: high energy per photon → ionises some atoms → fluorescence.
X-ray: penetrates soft tissue, absorbed by dense matter (bone) → image contrast.
Gamma: very high energy → kills cells, deeply penetrating → sterilisation.

Radio = broadcasting.
Micro = cooking + satellite.
IR = heating + night vision.
Visible = optical fibres + photography.
UV = fluorescent lamps + bank-note detection.
X-ray = bone imaging + airport security.
Gamma = sterilising + radiotherapy.

See the full worked example for the electromagnetic spectrum →

Detrimental effects + protection (spec 3.13)

Tissue-level damage by band.

Each band has a DIFFERENT mechanism for harming tissue:

Microwaves — INTERNAL HEATING. Microwaves absorbed by water inside cells → cellular damage / burns from inside out. Microwave ovens have metal mesh in the door (holes smaller than $\lambda$ ) to keep the radiation in.
Infrared — SKIN BURNS. Absorbed at the SURFACE → surface skin burns. Use of insulating gloves / safety screens near hot objects.
Ultraviolet — SURFACE CELL DAMAGE AND BLINDNESS. UV photons damage DNA in surface skin cells → sunburn, premature ageing, skin cancer. UV damage to the retina can cause blindness. Protection: sunscreen, hats, UV-blocking sunglasses, protective clothing, avoid midday sun.
X-rays / Gamma rays — CANCER AND MUTATION. Very high-energy photons IONISE atoms inside cells → damaged DNA → mutations → cancer. Workers wear LEAD APRONS; sources are stored in lead-lined containers; patients receive only short exposures.

Spec 3.13 phrasing to memorise. "describe simple protective measures against the risks". The protective measures expected:

Lead aprons / lead-lined containers — for X-ray and gamma.
Sunscreen, hats, sunglasses, long sleeves — for UV.
Microwave-oven metal mesh / interlock so oven cannot run with door open — for microwaves.
Insulating gloves / screens / distance — for IR.

Examiner pattern. A favourite question asks for the HAZARD and a SPECIFIC protective measure. Cluster your answer: hazard (one tissue-level effect) + matching protection.

Microwave → internal heating; protection = oven mesh.
IR → surface burns; protection = gloves / distance.
UV → cell damage + blindness; protection = sunscreen + sunglasses.
X-ray / gamma → cancer / mutation; protection = lead aprons / shielding.

See the full worked example for the electromagnetic spectrum →

Microwave vs IR heating — frequent comparison item

Inside-out (micro) vs outside-in (IR).

A favourite Paper-1 4-mark item compares MICROWAVE and IR heating of food:

Microwave (inside-out). Microwaves penetrate food and are absorbed primarily by WATER molecules INSIDE. Water molecules vibrate → kinetic energy spreads as heat. Food heats from within.

Infrared (outside-in). IR is absorbed at the SURFACE. Surface heats first; heat then CONDUCTS inwards. Toasters, grills and electric heaters work this way.

Hazard contrast. Microwave hazard = INTERNAL heating of body tissue (e.g. eyes, blood-rich tissue). IR hazard = SKIN/SURFACE burns.

Practical implication. Microwaves cook unevenly because thicker pieces don't fully absorb the wave before it reaches the centre — hence the rotating turntable in domestic ovens. IR grills can leave the inside cold even when the surface is browned.

Microwave: absorbed by water → heats inside out.
IR: absorbed at surface → heats outside in.
Both can cook food; hazards differ.

See the full worked example for the electromagnetic spectrum →

How it’s examined

EM spectrum content is on every 4PH1 paper, usually 6-10 marks across Paper 1 and Paper 2. Highest-frequency items: ordering by wavelength/frequency (2-3 marks); matching named wave to its named use (3-5 marks); describing detrimental effects + protection (4-5 marks); $v = f\lambda$ calculations using $c$ (3-4 marks).

Sources: Pearson Edexcel International GCSE Physics 4PH1 specification — Issue 4, September 2024 (valid for 2026 onwards); Pearson Edexcel 4PH1 Examiner Reports 2022-2024; 4PH1/1P May/Jun 2024 question paper and mark scheme; 4PH1/1P January 2024 question paper and mark scheme. Last reviewed 2026-05-12.

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Step-by-step worked examples — The Electromagnetic Spectrum

Step-by-step solutions to past-paper-style questions on the electromagnetic spectrum, written exactly the way a tutor would explain them at the board.

1Ordering the EM spectrum (4 marks, Paper 1)
Core• Adapted from 4PH1/1P May/Jun 2024• spectrum, ordering, spec-3.10, spec-3.11, Paper 1
Question
Place the following waves in order of INCREASING frequency: gamma, infrared, microwaves, radio, ultraviolet, visible, X-ray. State the wave speed of all of these waves in vacuum. (4 marks)
Step-by-step solution
1. Step 1
  Rule (spec 3.10, 3.11). From LOWEST frequency (longest wavelength) to HIGHEST frequency (shortest wavelength): radio → micro → infrared → visible → ultraviolet → X-ray → gamma.
2. Step 2
  Ordering. radio, microwaves, infrared, visible, ultraviolet, X-ray, gamma.
3. Step 3
  Wave speed (spec 3.10). ALL members of the electromagnetic spectrum travel at the same speed in vacuum: $c = 3 \times 10^{8}\,\text{m/s}$ .
Answer
Increasing frequency: radio, micro, infrared, visible, ultraviolet, X-ray, gamma. All travel at $3 \times 10^{8}$ m/s in vacuum.
Examiner tip
Edexcel mark schemes accept any clear ordering (left-to-right or top-to-bottom list). One mark is lost for any swap. A common mnemonic is 'Roman Men Invented Very Unusual X-ray Guns'. Memorise the speed value to ONE significant figure as $3 \times 10^{8}$ m/s.
2Uses of EM waves — match the application (5 marks, Paper 1)
Core• Adapted from 4PH1/1P January 2024• uses, spec-3.12, Paper 1
Question
State the most appropriate part of the electromagnetic spectrum used for each of the following applications, and briefly explain why it is suitable: (a) cooking food in a microwave oven, (b) sterilising surgical instruments, (c) communication between a TV remote control and a TV, (d) imaging broken bones, (e) broadcasting national television. (5 marks)
Step-by-step solution
1. Step 1
  (a) Microwaves. Microwaves at ~2.45 GHz are strongly absorbed by water molecules in food, heating it from within.
2. Step 2
  (b) Gamma rays (or UV). Spec 3.12 names gamma for sterilising food and medical equipment — gamma kills bacteria and is highly penetrating.
3. Step 3
  (c) Infrared. TV remotes emit short pulses of IR (~940 nm) — cheap LEDs, line-of-sight signalling.
4. Step 4
  (d) X-rays. X-rays pass through soft tissue but are absorbed by dense bone — a film/detector records the shadow.
5. Step 5
  (e) Radio waves. Radio waves diffract around obstacles and travel long distances → ideal for broadcasting.
Answer
(a) Microwaves; (b) Gamma rays; (c) Infrared; (d) X-rays; (e) Radio waves.
Examiner tip
Edexcel mark schemes for spec 3.12 award 1 mark per correct pairing. Adding the REASON earns extra marks on extended-response variants. Be careful about gamma vs UV for sterilisation — spec 3.12 explicitly lists GAMMA for sterilising. UV is named for fluorescent lamps and detecting forged bank notes.
3Detrimental effects of UV radiation (5 marks, Paper 1)
Extended• Adapted from 4PH1/1P May/Jun 2024• hazards, spec-3.13, Paper 1
Question
Sunbathing exposes the skin to ultraviolet radiation. (a) State TWO detrimental effects of prolonged UV exposure on the human body. (b) Describe TWO protective measures a person could take when sunbathing. (5 marks)
Step-by-step solution
1. Step 1
  (a) Effect 1. UV damages the OUTER LAYER of cells (epidermis) → causes sunburn and accelerated skin ageing.
2. Step 2
  Effect 2. Prolonged exposure causes DNA mutations → increased risk of SKIN CANCER (and damage to the retina → possible blindness).
3. Step 3
  (b) Protection 1. Apply SUNSCREEN containing UV-blocking chemicals (high SPF).
4. Step 4
  Protection 2. Wear protective clothing / a wide-brimmed hat and UV-blocking SUNGLASSES; avoid being out in midday sun.
5. Step 5
  Examiner phrasing. Spec 3.13 wording: 'UV radiation can cause damage to surface cells and blindness'. Use these exact phrases.
Answer
(a) (i) Damage to surface skin cells → cancer/burns/ageing; (ii) damage to retina → blindness. (b) Sunscreen + protective clothing/sunglasses.
Examiner tip
Edexcel mark scheme keywords for spec 3.13 UV: 'surface cells', 'skin cancer', 'blindness'. Avoid vague 'sun damage'. Mention SPECIFIC protective measures — 'be careful' earns 0 marks.
4Comparing microwave and infrared heating (4 marks, Paper 1)
Extended• heating, spec-3.12, spec-3.13, Paper 1
Question
Microwave ovens and infrared grills can both cook food. Compare how each transfers energy to food, and state the chief safety hazard of each. (4 marks)
Step-by-step solution
1. Step 1
  Microwave heating. Microwaves are absorbed primarily by WATER molecules INSIDE the food → water molecules vibrate → kinetic energy spreads as heat through the food. Heats from within.
2. Step 2
  Infrared heating. IR is absorbed by the SURFACE of the food → surface heats first; heat then conducts inwards. Heats from outside in.
3. Step 3
  Microwave hazard (spec 3.13). Internal heating of body tissue (water in cells) — burns / damage to internal organs.
4. Step 4
  Infrared hazard (spec 3.13). Surface burns / skin burns from absorption at the surface.
Answer
Microwave: absorbed by water inside food → heats from within; hazard = internal tissue heating. IR: absorbed at surface → heats outside in; hazard = surface burns.
Examiner tip
Examiners look for the CONTRAST: 'inside' (microwave) vs 'outside / surface' (IR). Spec 3.13 detrimental effects: microwave = internal heating of body tissue; IR = skin/surface burns; UV = surface cells damage/blindness; gamma = cancer/mutation. Memorise each pairing.

Key Formulae — The Electromagnetic Spectrum

The formulae you need to memorise for the electromagnetic spectrum on the Pearson Edexcel IGCSE 4PH1 paper, with every variable defined in plain English and a note on when to use it.

EM wave speed in vacuum (spec 3.10)
$c = 3 \times 10^{8}\ \text{m/s}$
When to use
$c$ is the speed of ALL members of the electromagnetic spectrum in vacuum. Use it in the wave equation $v = f\lambda$ (spec 3.5) for any EM wave problem.

Key Definitions and Keywords — The Electromagnetic Spectrum

Definitions to memorise and the exact keywords mark schemes credit for the electromagnetic spectrum answers — sharpened from recent examiner reports for the 2026 Pearson Edexcel IGCSE 4PH1 sitting.

Electromagnetic spectrum (spec 3.10)
Examiner keyword
A continuous range of transverse waves, all travelling at $3 \times 10^{8}$ m/s in vacuum. In order of decreasing wavelength (increasing frequency): radio, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays.
Visible light (spec 3.11)
Examiner keyword
The very narrow band of the EM spectrum that the human eye can detect, wavelengths roughly 400 nm (violet) to 700 nm (red). In order of INCREASING wavelength: violet, indigo, blue, green, yellow, orange, red.
Radio waves use (spec 3.12)
Broadcasting (radio, TV) and communications — long wavelength diffracts around obstacles and over the horizon.
Microwaves use (spec 3.12)
Cooking food (~2.45 GHz absorbed by water) and satellite communications (microwave signals penetrate the atmosphere).
Infrared use (spec 3.12)
Electrical heaters, cooking (grills), night-vision cameras, short-range remote controls and optical-fibre communications (also visible).
Ultraviolet use (spec 3.12)
Fluorescent lamps (UV excites phosphor → visible glow), sterilising water, detecting forged bank notes (security marks).
X-ray use (spec 3.12)
Medical imaging of bones (X-rays absorbed by dense bone, transmitted through soft tissue) and security scanning at airports.
Gamma ray use (spec 3.12)
Sterilising food and medical equipment (gamma kills bacteria) and treating cancer (radiotherapy targets tumours).

Common Mistakes and Misconceptions — The Electromagnetic Spectrum

The traps other students keep falling into on the electromagnetic spectrum questions — taken from recent Pearson Edexcel IGCSE 4PH1 examiner reports and mark schemes — and how to avoid them.

✕Reversing the order of frequency vs wavelength
4PH1 Examiner Reports 2022-2024
Why it happens
Forgetting that $v = f\lambda$ with $v$ fixed means $f$ and $\lambda$ are INVERSELY related.
How to avoid it
Memorise one direction (say, increasing frequency: radio → gamma) and remember the OPPOSITE ordering applies to wavelength.
✕Quoting visible light colours in the wrong order
Why it happens
Some textbooks list red → violet (decreasing wavelength), others violet → red.
How to avoid it
By WAVELENGTH (longest first): red, orange, yellow, green, blue, indigo, violet ('Richard Of York...'). By FREQUENCY (lowest first): the SAME order — red → violet. Edexcel mark schemes accept either ordering as long as it's clearly labelled.
✕Saying UV is used for sterilisation (when spec 3.12 names gamma)
4PH1 Examiner Reports 2022-2024
Why it happens
Both UV and gamma kill bacteria.
How to avoid it
Spec 3.12 explicit pairings: UV → fluorescent lamps + bank notes; GAMMA → sterilising. Use the spec example.
✕Vague answers about hazards ('it's dangerous')
4PH1 Examiner Reports 2022-2024
Why it happens
Not memorising the spec 3.13 pairings.
How to avoid it
Memorise each pairing: microwave → internal tissue heating; IR → skin burns; UV → cell damage / cancer / blindness; gamma/X → mutation, cancer.
✕Saying EM waves all travel at $3 \times 10^{8}$ m/s in ALL materials
Why it happens
The phrase 'all EM waves travel at c' gets quoted out of context.
How to avoid it
Spec 3.10 says 'in vacuum'. EM waves SLOW DOWN in glass, water etc. — this is what causes refraction (spec 3.17).

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

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The Electromagnetic Spectrum — frequently asked questions

The things students keep getting wrong in this sub-topic, answered.

The Electromagnetic Spectrum

Short Study Notes in the form of Slides

Detailed Study Notes

What you’ll learn

How it’s examined

1Ordering the EM spectrum (4 marks, Paper 1)

2Uses of EM waves — match the application (5 marks, Paper 1)

3Detrimental effects of UV radiation (5 marks, Paper 1)

4Comparing microwave and infrared heating (4 marks, Paper 1)

EM wave speed in vacuum (spec 3.10)

Electromagnetic spectrum (spec 3.10)

Visible light (spec 3.11)

Radio waves use (spec 3.12)

Microwaves use (spec 3.12)

Infrared use (spec 3.12)

Ultraviolet use (spec 3.12)

X-ray use (spec 3.12)

Gamma ray use (spec 3.12)

✕Reversing the order of frequency vs wavelength

✕Quoting visible light colours in the wrong order

✕Saying UV is used for sterilisation (when spec 3.12 names gamma)

✕Vague answers about hazards ('it's dangerous')

✕Saying EM waves all travel at 3×1083 \times 10^{8}3×108 m/s in ALL materials

Practice questions

Past paper style quiz

Assess your understanding

Video lesson

The Electromagnetic Spectrum — frequently asked questions

✕Saying EM waves all travel at $3 \times 10^{8}$ m/s in ALL materials