Question

Photoelectrons with a maximum speed of 8.00 • 106 m/sec are ejected froma surface in the presence of light with a frequency of 6.32 · 1014Hz. If themass of an electron is 9.10 . 10-31 kg, calculate the maximum kineticenergy of a single electron, in joules.a. 3.64 x 10-24 Jb. 2.88 x 10-16 Jc. 5.82 x 10-17 Jd. 2.91 x 10-17 J

Answer 1

The kinetic energy is given by:

$K=\frac{1}{2}mv^2$

We know the mass and the maximum speed, plugging their values in the expression above we have:

$\begin{gathered} K=\frac{1}{2}(9.1\times10^{-31})(8\times10^6)^2 \\ K=2.91\times10^{-17}\text{ J} \end{gathered}$

Therefore, the answer is d.