Final answer:
An X-ray is a high energy electromagnetic radiation that can penetrate substances and record images on photographic film.
Step-by-step explanation:
An X-ray is a form of high energy electromagnetic radiation with a short wavelength that is capable of penetrating solids and ionizing gases. It is used in medicine as a diagnostic aid to visualize body structures such as bones.
Photographic film is the most common detector of ionizing radiation, including X-rays. When X-rays pass through the material and strike the film, they cause a chemical change that creates an image on the film.
Therefore, an X-ray can be considered as a beam of energy that has the power to penetrate substances and record image shadows on a photographic film.