Question

In a photoelectric effect experiment, electrons emerge from a copper surface with a maximum kinetic energy of 1.10 eV when light shines on the surface. The work function of copper is 4.65 eV.
Which one of the following values is closest to the wavelength of the light?

A) 220 nm

B) 150 nm

C) 360 nm

D) 1100 nm

Answer 1

Answer:A) 220 nm

Explanation:

Given

Maximum Kinetic Energy $K.E.=1.10 eV$

Work Function $W=4.65 eV$

from Einstein Equation

$h\mu =W+K.E.$

$h\cdot \frac{c}{\lambda }=W+K.E.$

$h\cdot \frac{c}{\lambda }=4.65+1.10$

$6.626\times 10^{-34}\cdot \frac{3\times 10^8}{\lambda }=5.75$

$1 eV=1.6\times 10^{-19} J$

thus $5.75 eV=9.2\times 10^{-19} J$

$\lambda =\frac{6.626\times 10^{-34}\time 3\times 10^8}{9.2\times 10^{-19}}$

$\lambda =216.06 nm\approx 220 nm$