*samples original signal (red) rebuilt signal (green)
Let's suppose we sample the sinusoidal signal (frequency f) with a sampling frequency of . This involves that the sampling period is equal to three quarters of the signal period. We verify that the most normal rebuilding of a sinusoide passing through the samples is the sinusoide with a frequency of f/3. This is an illustration of the frequency aliasing in the temporal domain.
You can test sinusoides respecting or not the sampling theorem
Playing with sinusoides 2
Flash animation - Temporal Domain