Secondary radiation is defined as

• A. Created when the x-rays come in contact with matter.
• B. X-rays that come from the tube head.
• C. Radiation that travels through space.
• D. Heat produced during exposure.

Answer: (A)

Secondary radiation is the photons produced when the primary x-ray beam interacts with matter, such as the patient or surrounding surfaces. When these photons strike matter, they can be scattered (like Compton scatter) or cause other interactions that release new x-ray photons in different directions. This is why the statement that it is created when x-rays come in contact with matter best captures the concept: the radiation arises from the interaction between the beam and matter, not from the tube head, not simply traveling through space, and not from heat.