You may have seen images, like the one shown above, on an airport's X-ray scanner computer screen. The colourful, abstracted, overlapping outlines seem almost cartoon-like, but they help security agents determine a bag's contents and potential danger. The scanner's bright palette is not arbitrary; each colour identifies a different atomic weight, isolating a range of densities and materials. The brightness of the colours indicates the thickness of each item. Here’s a breakdown of the colours produced by the X-ray and what they highlight:
Orange: Organic materials like clothing, food, paper, and explosives.
Blue: Inorganic materials like glass, metals and ceramics.
Green: Mixed substances, a combination of organic and inorganic materials like aluminum, silicon and glass.
Red: Materials with little or no resistance to X-rays, such as cloth, carton, or paper.