Augmented reality (AR) learning scenarios with see-through smartglasses create a wearable education technology providing active access to various additional information without distracting from the physical interaction with reality. We already have introduced such an AR version of a standard physics experiment of introductory lab courses on heat conduction in metals, using real physical data from external sensors for analyzing and displaying thermal phenomena in real-time. Besides a direct feedback, ensuring that students get an immediate impression of the effects of the experimental parameters, this scenario is also able to visualize invisible physical processes, using false-color representations to show the temperature of the apparatus. In a previous study conducted in an introductory STEM laboratory, we were able to show that such an AR learning environment indeed is suitable to foster learners' conceptual understanding of thermal phenomena. In the current paper we focus on the question how learners can benefit from such a scenario by influencing cognitive load (CL). In a second study we use the cognitive load scale (CLS) to discriminate the different types of learners' CL. We confirmed the structure of the scale by a factor analysis, finding three factors corresponding to the three types of CL, each with high reliability. Moreover, we were able to show that with our AR scenario extraneous load could significantly be reduced, compared to a non augmented traditional setup.