Answer
$5.6\times 10^{4}$
Work Step by Step
As the e reflection coefficient $R=0.112$, we can say that an electron has $0.112\%$ chance of being reflected.
The incident beam sends $5.00\times10^5$ electrons against
the potential step.
Therefore, the number of electrons will be reflected is
$=5.00\times10^5\times \frac{0.112}{100}\times100$
$=5.6\times 10^{4}$
