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3.3.1Waves

Electromagnetic Waves — Cambridge IGCSE Physics 0625 Revision Notes & Topical Questions

5 min read 8 parts Lesson 26 of 35 1 quiz

📚 Cambridge IGCSE Physics 0625 Hub / Topical Revision
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Curriculum Equation Key Wave Speed & Doppler Effect FormulasFast Exam Solution
v = f × λ | f_obs = f × (v ± v_o) / (v ∓ v_s) | T = 1 / f
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Lesson summary

3.3.1 Electromagnetic Waves — IGCSE PHYSICS notes: State the order, common properties and speed of electromagnetic waves.Definition — transverse waves that transfer energy from the source of the waves to an absorberNature — oscillations of electric and magnetic fields, not of par…

  • Wavelength and frequency
  • Direction of change
  • Memory aid
  • Interaction with matter
  • In a vacuum
  • Unit conversions

Part 1 of 6What electromagnetic waves are

Definition
  • Definition transverse waves that transfer energy from the source of the waves to an absorber
Nature
  • Nature oscillations of electric and magnetic fields, not of particles
Spectrum
  • Spectrum a continuous family of waves arranged by wavelength or frequency

Part 2 of 6The spectrum in order

Longest to shortest wavelength
  • Radio waves
  • Microwaves
  • Infrared
  • Visible light (red, orange, yellow, green, blue, indigo, violet)
  • Ultraviolet
  • X-rays
  • Gamma rays
Wavelength and frequency
  • Wavelength and frequency long wavelength means low frequency and vice versa
Direction of change
  • Direction of change wavelength falls and frequency rises from radio waves to gamma rays
Memory aid
  • Raging Martians Invaded Venus Using X-ray Guns
Size link
  • Size link radio waves are big and gamma rays come from tiny atoms (short wavelength)
    • (long wavelength)

Part 3 of 6Properties common to all

Transverse
  • Transverse all electromagnetic waves are transverse
Vacuum
  • Vacuum all can travel through a vacuum
Speed
  • Speed all travel at the same high speed in a vacuum
Value
  • 3.0 × 108 m/s, which is about the same in air

Part 4 of 6How the regions differ

Wavelength and frequency
  • Wavelength and frequency differ between regions
Energy
  • Energy increases as frequency increases
Interaction with matter
  • Interaction with matter different regions are absorbed, reflected or transmitted differently, which gives different uses and dangers

Part 5 of 6Using the wave equation

Equation
  • Equation v = fλ applies to every electromagnetic wave
In a vacuum
  • In a vacuum v is 3.0 × 108 m/s, so a higher frequency means a shorter wavelength
Unit conversions
  • Unit conversions convert kHz, MHz and nm to SI units first

Part 6 of 6More from the specification

1Photovoltaic solar cells
  • Photovoltaic solar cells semiconductor photovoltaic cells absorb incident solar electromagnetic radiation, promoting electrons across band gaps into electric circuits.
2Optical fibres and cellular communication
  • Optical fibres and cellular communication digital data pulses transmitted through low-loss optical fibres route cellular traffic across metropolitan fiber networks.
3Artificial satellite
  • A man-made object orbiting a body in space.
4Digital signal
  • Signal that has only two states, 1 and 0
5Analogue
  • Instrument displaying a quantity by pointer position or liquid level on a scale.
6Satellite
  • A body that orbits a larger one; the Moon is the Earth's natural satellite.
7Radiation
  • Transfer by electromagnetic waves, requiring no medium
8Geostationary
  • Orbiting with a period of 24 h above the equator, so staying above one point.
9Transmission
  • Sending electricity along power cables from the power station to consumers.
10Analogue signal
  • Signal that varies continuously and can take any value
11Geostationary satellite
  • Satellite orbiting above the equator in 24 hours at 36 000 km
12Optical fibre
  • Thin transparent strand that guides light by TIR

Key terms

TermMeaning
Electromagnetic spectrumContinuous family of waves from radio waves to gamma rays
Radio waveLongest-wavelength electromagnetic wave
Gamma rayShortest-wavelength, highest-frequency electromagnetic wave
Speed of EM waves3.0 × 108 m/s in a vacuum
Transverse waveWave whose vibration is at right angles to its direction of travel

Avoid these mistakes

1
Saying EM waves are longitudinal — they are transverse.
2
Saying EM waves have different speeds in a vacuum — all travel at 3.0 × 108 m/s.
3
Reversing the order of the spectrum — gamma rays have the shortest wavelength.
4
Saying wavelength and frequency both rise together — one rises as the other falls.

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