Effect of aliasing when sampling at higher rate
The name of this effect is Spectral Leakage. Remember the relation
$$\frac{k}{N} = \frac{F}{F_S}$$
where $k$ is the bin number, $N$ is the FFT size, $F$ is the continuous frequency in Hz and $F_S$ is the sample rate in Hz. It can be seen that $k$ varies from $-N/2$ to $N/2-1$ (or from $0$ to $N-1$). So there are only $N$ continuous frequencies $F$ for which you will get a single impulse in discrete frequency domain.

So in the first figure, the frequency of the signal contains an exact integer number of periods within the FFT duration and hence the correlation of other DFT sinusoids with the signal is zero. In the second figure, the signal span is not equal to the integer number of periods that violates the orthogonality requirement. Hence, the correlation of different DFT sinusoids appears as leakage around the true frequency.