Final answer:
The type of dye used to distinguish water from fuel during a visual sample is a fluorescent dye called fluorescein. It emits a fluorescent green color under ultraviolet light, providing a clear contrast to detect the presence of water in fuel.
Step-by-step explanation:
During a visual sample to distinguish water from fuel, a commonly used fluorescent dye called fluorescein is utilized. Fluorescein is highly effective because when it is diluted in water, it absorbs light and subsequently emits a bright, fluorescent green color when exposed to ultraviolet radiation (UV light). This characteristic allows for a clear contrast for those inspecting the sample, thereby facilitating the easy differentiation between water and fuel. When observing under UV light, the degree of fluorescence can show the concentration of the dye, ranging from more dilute to more concentrated solutions.
Illustrate how a fluorescent dye diffuses in water and reassure the concept. Furthermore, describes how fluorescent dyes, when absorbed by biological cells such as bovine pulmonary artery endothelial cells, emit brilliant colors under a fluorescence microscope. This concept is relevant as it further explains the utility of fluorescent dyes under UV light for various applications.