The subject of Oscilloscope is chosen because is the machinery that demonstrates our prior lesson on Bandwidth and Frequency. The o-scope measures frequency. We've all seen the box that beeps in hospital rooms with the wave form moving across the small screen; this is called a cathode ray oscilloscope (CRO). The on screen graph has a vertical Y axis, which measures the amplitude; and a horizotal X axis that notes the time it takes to beep again. Thus, the o-scope measures the frequency of the amplitude of a wave over time.
Oscilloscopes are used in the automotive industry for diagnostics, in medicine to display the waveform of a heartbeat as an electrocardiogram. They are, also, used in telecommunications, in the sciences and in engineering. Today's o-scopes are digital (DSO-Digital Storage Oscilloscope). DSOs utilize general purpose digital computers to process and display waveforms at a much lower cost.