A model estimates that the initial number of photons in an X-ray beam…

Question

Prompt

A model estimates that the initial number of photons in an X-ray beam is

800

when the beam reaches the surface of a certain material. The model also estimates that when the beam passes through this material, the number of photons in the beam decreases by

50%

for each

7 millimeters

of the material the beam passes through. Which equation represents this model, where

I

is the estimated number of photons in the beam when the beam reaches a point

x millimeters

from the surface?

I = 800 (7)^{\frac{x}{2}}

I = 800 (0.5)^{x}

I = 800 (2)^{\frac{x}{7}}

I = 800 (0.5)^{\frac{x}{7}}