Final answer:
Ultrasonic waves are used in nondestructive testing to find defects within steel by emitting waves that reflect back when hitting a density change, such as cracks. These reflections are analyzed to pinpoint the location and size of defects while the waves' attenuation helps assess material properties in solid state physics.
Step-by-step explanation:
Ultrasonic waves are a powerful tool employed in nondestructive testing to detect defects within a solid piece of steel. These high-frequency sound waves are capable of locating discontinuities or changes in material properties which are indicative of defects such as cracks or voids. The process involves transmitting ultrasonic waves into the steel, where they travel until they encounter a boundary or change in material density. The key factor is the reflection of these waves: they reflect well from any significant change in density. When a wave hits a defect, it reflects back to the surface where it can be detected by a transducer.
The time it takes for the reflection to return, as well as the amount of energy lost, help to determine the location and size of the defect. This method is also valuable for measuring the thickness of coatings without the need for direct access or destruction of the part being inspected. In the field of solid state physics, ultrasound's attenuation is tied to various physical characteristics providing insights into structural changes and properties of materials.