Question

Photons of wavelength 199 nm are incident on a metal plate in a photocell, and electrons are ejected. A stopping potential of 1.10 V is able to just prevent any of the ejected electrons from reaching the opposite electrode. What is the maximum wavelength of photons that will eject electrons from this metal

Answer 1

λ = 11.29 x 10⁻⁷ m = 1129 nm

Step-by-step explanation:

According to the law of conservation of energy:

`Photon\ Energy = Energy\ Applied\ by\ Stopping\ Potential\\\\(hc)/(\lambda) = eV\\\\\lambda = (hc)/(eV)`

where,

λ = maximum wavelength = ?

h = Plank's Constant = 6.625 x 10⁻³⁴ J.s

c = speed of light = 3 x 10⁸ m/s

e = charge on electron = 1.6 x 10⁻¹⁹ C

V = stopping poteential = 1.1 V

Therefore,

`\lambda = ((6.625\ x\ 10^(-34)\ J.s)(3\ x\ 10^8\ m/s))/((1.6\ x\ 10^(-19)\ C)(1.1\ V))`

λ = 11.29 x 10⁻⁷ m = 1129 nm