For work to be considered done by a physicist, it must involve the application of physics principles and concepts to solve a problem or answer a research question. This can involve theoretical work, such as mathematical modeling, or experimental work, such as designing and conducting experiments to test hypotheses.
An example of work done by a physicist would be the design and analysis of experiments to study the properties of a new material. This could involve developing a theoretical model to predict the behavior of the material, designing and building experimental apparatus, conducting experiments, and analyzing the resulting data using statistical and mathematical techniques. The physicist would use their knowledge of physics principles and concepts to interpret the data and draw conclusions about the properties of the material.