Atomic Structure, Electron Configurations, and the Hydrogen Spectrum

The maximum energy required to cause the photoelectric effect in potassium metal is 3.68 × 10^{-19} J. What is the threshold frequency ($\nu_0$) for potassium? (Use $E = h\nu$ and $h = 6.626 \times 10^{-34}$ J·s)

A photon with energy $4.00 \times 10^{-19}$ J strikes a potassium surface. If the work function is $3.68 \times 10^{-19}$ J, what is the velocity of the emitted electron? (Use $E_{kinetic} = E_{photon} - \phi$ and $E_{kinetic} = \frac{1}{2}mv^2$, $m = 9.11 \times 10^{-31}$ kg)

The Lyman series of the hydrogen spectrum can be represented by the equation $\frac{1}{\lambda} = 1.097 \times 10^{7} \left(1 - \frac{1}{n^2}\right)$, where $n = 2, 3, ...$. What is the wavelength of the transition from $n = 3$ to $n = 1$?