Long description

This graph depicts a sine wave. It shows a series of regularly spaced, alternating peaks and troughs. There are nine cycles in total. The sine wave is blue and is labelled as ‘under-sampled sine wave’.

Eleven sampling points are shown on the sine wave, represented by dots at regular intervals. The dots are joined to form another smooth sine wave, this time drawn in red, which is labelled ‘alias signal’. The alias signal has only one cycle compared with the nine cycles of the original sine wave.