Interdisciplinary physics is a category of physics that applies the fundamentals of this science to subjects in other disciplines, thereby allowing a new perspective on those problems. This is sometimes referred to as applied physics, because it involves applying physics to other disciplines. As physics is not limited in its applications in principle, this category is most useful as an academic major and designation for degrees. Different schools allow various other majors to be combined with physics in their interdisciplinary physics programs.
The first and most important thing to understand is that interdisciplinary physics is an approach, not a different topic for physics. No subject is naturally more suited to physics than others, but some topics are traditionally covered by other disciplines. As physics studies the makeup of the universe, any subject could be within its purview. Topics like biological physics, for example, are often viewed as a marriage of biology and physics because of the special forces at work in biological contexts.
All hard sciences study the same materials from different perspectives, and many people believe that combining these perspectives can yield more fruitful research. As such, chemical physics and biological physics are both popular degrees. In these cases, research can be informed by both disciplines, yielding potentially valuable solutions to problems. Understanding the physics underlying chemistry, for example, can allow a more nuanced understanding of chemical processes.
In some cases, interdisciplinary physics can also enrich the field of physics by providing a more detailed understanding of its basic principles. Having a deep understanding of mathematics can often suggest interesting research in physics, as these two disciplines are so closely tied together. Likewise, a combination with computer science or engineering can be used to either produce interesting research in physics or create new models for use in physics.
As a degree, interdisciplinary physics is usually offered at the undergraduate level. At the graduate level, physics is often so focused that an interdisciplinary program is unfeasible or unnecessary. Even so, there are interdisciplinary programs that combine physics with teaching, which are primarily designed for people involved in physics education at the pre-college level.
Any discipline can be combined with physics to create an interdisciplinary physics program. While it is common to combine other sciences with physics, some schools allow a union with writing, political science, and other traditionally social sciences. In general, the result of these unions must enrich both disciplines in order for a school to consider the program a worthwhile degree.