Radiography is an imaging technique using X-rays to view the internal structure of an object. To create the image, a beam of X-rays, a form of electromagnetic radiation, is produced by an X-ray generator and is projected toward the object. A certain amount of X-ray is absorbed by the object, dependent its density and composition. The X-rays that pass through the object are captured behind the object by a detector (either photographic film or a digital detector). The generation of flat two dimensional images by this technique is called projectional radiography. Computed tomography (CT scanning) is where multiple 2D images from different angles undergo computer processing to generate 3D representations. Applications of radiography include medical (or "diagnostic") radiography and industrial radiography. Similar techniques are used in airport security (where "body scanners" generally use backscatter X-ray).