eigenvalues and eigenvectors of $vv^T$
I'm reading an article concerning the matrix
$$s s^T + bI,$$
where $s$ is a vector of length $N$, $b$ is a real scalar and $I$ is the unit matrix. $s^T$ is the transpose of $s$.
The article states that the first eigenvalue is $E_s+b$, and the rest are $b$. $E_s$ denotes the signal energy of $s$, i.e.
$$E_s = s^2(1)+s^2(2)+\cdots+s^2(n)$$
How can these eigenvalues be found?