Which of the following factors influences the penetration power of X-rays?

The penetration power of X-rays is primarily influenced by the kilovolt peak (kVp) settings during the radiographic exposure. The kVp setting determines the energy of the X-rays produced; higher kVp values result in higher energy X-rays that possess greater penetrating power. This means they can pass through denser materials more effectively than lower energy X-rays. Consequently, adjusting the kVp setting allows for control over the contrast and overall quality of the radiographic image, as well as the ability to penetrate varying thicknesses and densities of the material being examined.

While the other factors listed can have an impact on the overall quality of the radiographic image, they do not directly influence the inherent penetrating ability of the X-rays themselves. For instance, different film types and radiographic film speeds affect image clarity and sensitivity rather than the penetration ability of the X-rays. Development temperature primarily influences the chemical response of the film during development, affecting image visibility and quality, but it does not alter the characteristics of the X-rays produced.