Zinc threshold frequency, 8.777*10^(14) to 1.185*10^(15) Hz
which corresponds to \(r\) of 4.0265*10^(-8) to 5.4362*10^(-8) m
The atomic radius of zinc is 134*10^(-12) = 1.34*10^(-10) m
Comparing \(r\) of the photon and atomic radius of zinc,
\(\frac{r}{R_{atomic}}\)=5.4362*10^(-8)/(1.34*10^(-10)) = 300 to 405
That means the photon and the orbital electron are interacting way before they come close to each other. This could happen, as one is a dipole with the positive end spinning and the negative charge in front, and the other, a negative charge.
We can of course define a interaction radius to be 300 to 400 times the atomic radius.
