A variety of assessment tools have become more prevalent in introductory physics courses as a way to enhance and assess conceptual learning. At the interface of modern physics and quantum mechanics, these tools are not presently as widely used. The Modern Physics course at American University presents an ideal opportunity for conceptual assessment given its somewhat atypical student composition. In this study both qualitative and quantitative measures of student understanding of a key concept in modern physics, the photoelectric effect are utilized. As a quantitative overall baseline for gain, the Quantum Physics Conceptual Survey (QPCS) was implemented [1]. A set of questions on the photoelectric effect that required both a quantitative and qualitative understanding of the photoelectric effect were then given on both the midterm and final exams. The results of the QPCS, and a subset of QPCS questions solely on the photoelectric effect, are statistically compared to the more focused approach for assessing the photoelectric effect. Additionally, correlations between subsets of the student population and their gains on the various assessments were investigated. The results from these assessment methods will be discussed in the larger context of how assessment measures can be maximized to enhance student understanding in a modern physics course. In particular this study shows how there may be a correlation between a student's background preparation, and their gain on different types of assessments.