Section 1 of 8What 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
Section 2 of 8The 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)
Section 3 of 8Properties 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
Section 4 of 8How 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
Section 5 of 8Using 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
Section 6 of 8More 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
Section 7 of 8Key terms
| Term | Meaning |
|---|---|
| Electromagnetic spectrum | Continuous family of waves from radio waves to gamma rays |
| Radio wave | Longest-wavelength electromagnetic wave |
| Gamma ray | Shortest-wavelength, highest-frequency electromagnetic wave |
| Speed of EM waves | 3.0 × 108 m/s in a vacuum |
| Transverse wave | Wave whose vibration is at right angles to its direction of travel |
Section 8 of 8Exam technique
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.
Transformer Golden Equations
Physics Standard
Transformer Turns Ratio & Efficiency
Ratio: Vp / Vs = Np / Ns = Is / Ip
- Step-up reduces grid thermal loss (
P = I2R). - Laminated core prevents eddy currents.