Which device would be primarily used for detecting X-rays?

Photographic film is the primary device used for detecting X-rays due to its ability to capture images of X-ray radiation. When X-rays pass through an object and hit the film, they expose it, thereby creating an image based on the varying densities of the materials that the X-rays have passed through. This process is foundational in both medical imaging and materials testing because it allows for the visualization of internal structures without invasive procedures.

Other devices listed, while effective for different forms of radiation or light, are not suitable for detecting X-rays in the same way. For example, a Geiger counter is effective for detecting ionizing radiation such as alpha and beta particles, but it is not specifically designed for X-rays and does not produce images. An infrared camera detects infrared radiation, which is outside the X-ray wavelength range, and a ultraviolet lamp emits UV light, which also does not cover the X-ray spectrum. Hence, among the options given, photographic film is uniquely suited for capturing the precise imaging required for X-ray detection.