Which pair of gamma ray sources are used for radiography?

Which pair of gamma ray sources are used for radiography?

• A. Cesium & Iridium
• B. Cobalt & Cesium
• C. Lead & Uranium
• D. Iridium & Cobalt

Answer: (D)

Radiography relies on gamma rays emitted by radioactive sources to image the inside of objects. The most practical and widely used pair for industrial radiography is cobalt-60 and iridium-192. Cobalt-60 emits high-energy photons (1.17 and 1.33 MeV), which provide strong penetration for thicker sections and larger welds, enabling fast exposure times. Iridium-192 releases multiple gamma lines in the lower energy range (roughly 0.3 to 0.7 MeV), which is well-suited for thinner sections and smaller components, and its source can be manufactured in compact, manageable form with a useful life that fits routine inspections. Together, they cover a broad range of applications and material thicknesses, which is why they are the standard pair for radiography. Other options don’t fit as sources: lead is shielding, uranium isn’t used as a routine radiography source, and cesium-137 isn’t the preferred pairing in typical practice.

Radiography relies on gamma rays emitted by radioactive sources to image the inside of objects. The most practical and widely used pair for industrial radiography is cobalt-60 and iridium-192. Cobalt-60 emits high-energy photons (1.17 and 1.33 MeV), which provide strong penetration for thicker sections and larger welds, enabling fast exposure times. Iridium-192 releases multiple gamma lines in the lower energy range (roughly 0.3 to 0.7 MeV), which is well-suited for thinner sections and smaller components, and its source can be manufactured in compact, manageable form with a useful life that fits routine inspections. Together, they cover a broad range of applications and material thicknesses, which is why they are the standard pair for radiography. Other options don’t fit as sources: lead is shielding, uranium isn’t used as a routine radiography source, and cesium-137 isn’t the preferred pairing in typical practice.