Ultra-violet light is shone on a zinc surface and photoelectrons are emitted. The sketch graph shows how the stopping potential \({V_s}\) varies with frequency \(f\).

Planck’s constant may be determined from the charge of an electron \(e\) multiplied by

A.     the \(x\)-intercept.

B.     the \(y\)-intercept.

C.     the gradient.

D.     the area under the graph.

C