Final answer:
The term describing the increased illumination from the input to the output phosphor in a photo multiplier tube due to the multiplication of light photons and image minification is known as 'gain'. Photo multipliers use the photoelectric effect to amplify the signal and are used in imaging technologies to process light into electrical signals.
Step-by-step explanation:
The increased illumination of the image in the context of the photomultiplier tube is due to the multiplication of light photons at the output phosphor compared to x-rays at the input phosphor, and the image minification from the input phosphor to the output phosphor. This process is known as the gain of the photomultiplier tube.
It leverages the photoelectric effect according to which the incoming light strikes a metal plate (the photocathode) and ejects an electron that subsequently hits the next dynode. Each dynode is set at a higher potential, thereby multiplying the electrons through successive stages, which results in an amplified electrical signal corresponding to greater illumination of the output image.
Photomultipliers are an essential component in various imaging technologies, including those used in medical imaging and research. They enable the detection and analysis of faint light signals, the conversion of those signals into strong electrical outputs that can be readily measured, and the construction of detailed images from these signals.