In a historical experiment to determine Planck’s constant, a metal surface was irradiated…

In a historical experiment to determine Planck’s constant, a metal surface was irradiated with light of different wavelengths. The emitted photoelectron energies were measured by applying a stopping potential. The relevant data for the wavelength (λ) of incident light and the corresponding stopping potential (V₀) are given below:

\[\begin{array}{c|c} \hline \lambda(\mu \mathrm{m}) & V_{\mathbf{0}} \text { (Volt) } \\ \hline 0.3 & 2.0 \\ 0.4 & 1.0 \\ 0.5 & 0.4 \\ \hline \end{array}\]
Given that c = 3 × 10⁸ m s^–1 and e = 1.6 × 10^–19 C, Planck’s constant (in units of J s) found from such an experiment is