In direct transmission, photons pass through material to reach which component?

• A. Gauge
• B. Detector
• C. Shield
• D. Source

Answer: (A)

Direct transmission means the photon beam travels straight through the material and is picked up by the gauge, which contains the detector that measures the transmitted photons. The gauge is the receiving element in this path, converting the photon flux into a readable signal to determine properties like density or thickness. The source is where photons originate, not where they arrive; the shield blocks photons, and a standalone detector outside the gauge wouldn’t be the component in the direct transmission path.