Final answer:
The student's question involves the application of physical principles such as fluid mechanics and optics to measure volume and study the behavior of light as it passes through different materials.
Step-by-step explanation:
The question at hand involves the application of physics principles to understand the behavior of an object in water or the optical properties of different materials. When considering a plastic glass with a square cross section filled with water, one is dealing with the concept of volume and measurements in the context of fluid mechanics.
Similarly, investigating the index of refraction of a gas within a plastic cube relates to the study of optics, particularly Snell's law and the behavior of light as it passes through different media. Lastly, measuring the volume of liquid with a graduated cylinder as outlined in Example 3.2.2.5, and considering the scenario of a large container of water with a hole, are both related to measurements and hydrodynamics within the scope of physics.