Step 1: Understanding the Concept:
Einstein's photoelectric equation relates the energy of the incident photon to the work function and the maximum kinetic energy of the electron: $h\nu = \phi_0 + K_{max}$.
Step 2: Detailed Explanation:
Since $K_{max} = eV_0$, we can rewrite the equation as:
$$eV_0 = h\nu - \phi_0 \implies V_0 = \left(\frac{h}{e}\right)\nu - \frac{\phi_0}{e}$$
This is in the form of a straight line equation $y = mx + c$, where the slope $m = \frac{h}{e}$.
Step 3: Final Answer:
The slope is $h/e$.