Answer
$6.25\times 10^{10}~~$ electrons strike the face of the glass tube each second.
Work Step by Step
We can write an expression for the current:
$I = 10~nA = 1.0\times 10^{-8}~C/s$
Let $n$ be the number of electrons that strike the face of the glass tube each second:
$n~q = 1.0\times 10^{-8}~C$
$n = \frac{1.0\times 10^{-8}~C}{q}$
$n = \frac{1.0\times 10^{-8}~C}{1.6\times 10^{-19}~C}$
$n = 6.25\times 10^{10}$
$6.25\times 10^{10}~~$ electrons strike the face of the glass tube each second.
