The intensity of current is defined as the quantity of charge Q that passes through a certain point in a time [tex]\Delta t[/tex]:
[tex]I= \frac{Q}{\Delta t} [/tex]
In our problem, the current is
[tex]I=134 \mu A= 134 \cdot 10^{-6}A[/tex] while the time interval is 16.0 s, so we can use the previous equation to find the total charge that strikes the target in this time:
[tex]Q=I \Delta t=(134 \cdot 10^{-6}A)(16.0 s)=2.1 \cdot 10^{-3}C[/tex]
We know that each proton carries a charge of [tex]q=1.6 \cdot 10^{-19}C[/tex], so we can find the number of protons that strike the target by dividing the total charge by the charge of a single proton:
[tex]N= \frac{Q}{q}= \frac{2.1 \cdot 10^{-3} C}{1.6 \cdot 10^{-19}C}=1.3 \cdot 10^{16} [/tex]
