Discussion Forum

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.

Given that c= 3x 10⁸ ms^-1 and e = 1.6x10¹⁹ C, Planck's constant  found from such an experiment is

Answer:

Explanation:

$\frac{hc}{\lambda}-\phi=eV_{0}$

$\frac{hc}{.3\times 10^{-6}}-\phi=2e$ ........i

$\frac{hc}{.4\times 10^{-6}}-\phi=1e$.........ii

Subtracting eq ii  from eq i

$hc\left(\frac{1}{0.3}-\frac{1}{0.4}\right)10^{6}=e$

$hc\left(\frac{.01}{0.12}\times 10^{2}\right)=e$

$h=.064\times 10^{-33}$

$h=6.4\times 10^{-34}$