A photomultiplier tube (PMT) is a highly sensitive device used to detect and amplify light signals. It works by converting incoming photons into electrons, which are then multiplied through a series of dynodes, resulting in a measurable electrical signal. PMTs are commonly used in applications such as nuclear physics, medical imaging, and particle detection. These tubes are particularly effective in low-light conditions, making them valuable in scientific research and various technologies. Their ability to detect single photons allows for precise measurements in experiments and instruments, including scintillation counters and fluorescence microscopy.