This Topic uses the sampling theory developed in the previous topics to analyse what happens when a pure sinusoid is sampled. The Topic considers two approaches: a time-domain and a frequency-domain approach. The frequency-domain approach considers the spectrum of the signal and seeks to plot the baseband spectrum, and then the spectral images at integer multiples of the sampling frequency. The components that are then between plus/minus half the sampling frequency are then those which will be seen at the output of the sampled data system after the reconstruction filter. The Topic considers the case of adequate and inadequate sampling. The video then moves on to consider a time-domain approach, which is somewhat less elegant than the frequency-domain approach, although of course it gives the sample result.