2026年6月国际A卷 · 第 9 题

The function \( f(x)=900(0.5)^{\frac{x}{12}} \)  gives the predicted intensity of a beam \( f(x) \) , in number of photons in the beam, x millimeters below the surface of a certain material. What is the best interpretation of  \( f(12)=450 \)?