How do fluorescent particles function in MPI?

Fluorescent particles function in Magnetic Particle Inspection (MPI) by glowing under ultraviolet (UV) light, which helps to reveal surface defects in the tested material. When a magnetic field is applied, these particles are attracted to areas of flux leakage, such as cracks or other discontinuities. When the UV light is applied, the fluorescent particles emit visible light, making it easier to detect these defects. This property enhances the contrast between the background and the defects, allowing for a more accurate inspection process.

The other options do not accurately describe the role of fluorescent particles in MPI. While some materials may change under heat, this is not relevant to their function in MPI. The statement about enhancing magnetization properties doesn't capture the actual use of these particles in defect detection. Additionally, indicating temperature variations is unrelated to the primary purpose of fluorescent particles within the context of magnetic particle inspection.