To determine the ratio of the slope of the stopping potential versus frequency plot for Gold to that of Aluminium, we need to use the photoelectric equation:
E = h \nu - \phi.
Where:
The stopping potential V_0 can be determined from the energy of the emitted electron as E = eV_0, where e is the charge of an electron. Therefore:
eV_0 = h \nu - \phi.
Rearranging the equation gives the relation for the stopping potential:
V_0 = \left( \frac{h}{e} \right) \nu - \frac{\phi}{e}.
Here, the slope of the stopping potential versus frequency plot is given by \left( \frac{h}{e} \right), which is invariant of the material's work function. Therefore, the ratio of the slopes is 1.
The correct answer is thus 1.