Matter: Using Water as an Example

In many chapters, we have had “light” as our central theme – as a phenomenon of nature, as our connection to the outer world, as an instrument for ophthalmological examinations, and as a tool for therapeutic interventions. In this chapter, we would like to discuss some concepts regarding the physics of matter that can be encountered frequently in practice. Since we do not wish to present the broad systematic physics of matter, we limit considerations to the fluid phase and explain some concepts, taking water as our example. However, water itself is also a topic. The more one deals with its properties, the more one gets the impression that this material was created to enable life and its development billions of years later.