Final answer:
Increased kilovoltage (kV) is the key factor that will increase the likelihood that a given x-ray will penetrate a material. It directly affects the energy of x-ray photons, allowing for deeper penetration into dense materials compared to the influence of milliamperes (mA) or exposure time.
Step-by-step explanation:
Increased kilovoltage (kV) will increase the likelihood that a given x-ray will penetrate a material. The energy of an x-ray photon is directly proportional to the kV setting of the x-ray tube: higher kV means more energetic x-rays, which can penetrate denser materials and cast clearer shadows on radiographic images. In contrast, milliamperes (mA) influence the number of x-ray photons produced, and exposure time determines how long the x-rays are produced, but neither directly augments the photons' penetrating power as kV does.
X-rays have high frequencies and energies, allowing them to penetrate materials that are opaque to visible light. This is especially useful in medical diagnostics, such as detecting bone fractures or imaging internal structures using contrast agents. However, it is important to minimize exposure due to the ionizing nature of x-rays which can damage biological cells.