Final answer:
Radiopaque objects or structures are dense and absorb X-rays, resulting in light gray or white areas on an X-ray film, indicating high density that X-rays cannot easily penetrate.
Step-by-step explanation:
The description provided corresponds to a situation where radiopaque objects are present in an X-ray. These are often dense structures, such as bones, that absorb many of the X-rays instead of allowing them to pass through and expose the film behind. Consequently, these areas appear as light gray or white on the X-ray film, indicating that fewer X-ray photons have reached the detector. Essentially, the greater the density of the material, the fewer the X-rays that can penetrate it, resulting in a clearer and lighter shadow on the film. This is the underlying principle that allows for the exceptional ability of X-rays to identify different structures within the human body, such as bone fractures or tumorous growths that differ significantly in density from the surrounding tissues.