Short Answer 
Airport scanners utilize advanced technologies like x-ray, gamma ray, and neutron scanning to inspect luggage for security threats and, occasionally, currency. Their primary goal is passenger safety, and modern currency features affect how it is detected during scans, complicating the process.
Step 1: Understanding Airport Scanners
Airport scanners, including both x-ray and three-dimensional scanners, are advanced machines designed to inspect luggage. They primarily aim to enhance safety by detecting security threats such as explosives or weapons. However, they can also reveal currency notes among other items.
Step 2: Technologies Utilized in Scanning
The functionality of these scanners relies on different types of technology to assess baggage contents. Common methods include:
- X-ray scanning that uses radiation to create images of the items inside bags.
- Gamma ray scanning capable of penetrating dense materials.
- Neutron scanning, which helps identify materials through their interaction with neutrons.
Step 3: Currency Detection and Security Features
While these scanning technologies can detect currency, their primary purpose is ensuring passenger safety rather than counting money. Modern currency contains security features, such as:
- Thin film interference in the design of U.S. currency.
- Diffraction gratings found in polymer notes, like those in Australia.
This interaction with light can impact how currency appears during scans, adding a layer of complexity to the scanning process.