 X-rays are being used to examine the human body without invasive surgery. But did you know that similar methods are also being used to determine the health of machines or structures? Methods that examine something without causing harm to it fall under the general term of non-destructive testing, or N-D-T for short. It is used to quickly evaluate materials in a component or system, let's say a bridge, without tearing it apart, rendering it unusable for a very long time. One popular testing method works a little bit like getting an X-ray, and is called radiography. To understand how it works, we need to have a quick look at electromagnetic radiation. Electromagnetic radiation can be described as a stream of particles without real size, called photons, each travelling in a wave-like pattern in various wavelengths at the speed of light. You may already know more about it than you might think. Radio waves, microwaves, but also the light visible to the human eye. That's all electromagnetic radiation which can be categorized in the electromagnetic spectrum. To be able to examine the inner workings of an object in detail, we need to look at the part of the spectrum with the shortest wavelengths. It's here where we can find X-rays and gamma rays. Unlike visible light, X and gamma ray beams can be sent through most objects while a part of them will be absorbed, depending on the object's density and composition. The rays that pass through the object are then captured by a detector, like a photographic film, creating a radiograph. This is only one of the many methods of non-destructive testing, but why is it so important? These testing methods can not only evaluate the property of material used in an object, but also detect flaws that might otherwise cause a lot of trouble. That's the reason why the IAEA is promoting the use of radiation-based non-destructive testing, by helping its member states train staff in applying the technology as well as providing necessary equipment. It is also providing know-how for analyzing paintings and other cultural heritage artifacts, but that's a whole other story. Thanks for watching, and if you want to know more about non-destructive testing, please click on one of the links next to the video or go to our website.