This chapter has laid the arithmetic foundation that keeps returning throughout the rest of the learning environment:
- A quantity is what you measure, the unit is the measure; always work in the SI system and write the units down.
- Frequency f (Hz) and period T (s) are each other's inverse: f = 1/T.
- Powers of 10 and prefixes (kilo, mega, giga, tera, milli, micro, nano) make large and small numbers manageable.
- The speed of light c ≈ 3 × 108 m/s links frequency and wavelength: c = f × λ, and makes distance measurement via travel time possible.
- Temperature in kelvin determines how much infrared radiation an object emits, and at which wavelengths.
- Azimuth, elevation and range fix the position of a target; the radial velocity is the velocity component along the line of sight and is what a Doppler radar actually measures.
With this toolbox in your pocket you can move on to the electromagnetic spectrum itself.