This dissertation focuses on three different populations of learners served by typical physics departments: STEM majors within a calculus-based introductory physics course, non-STEM majors within a general education survey astronomy course (Astro 101), and in- service STEM teachers within a professional development workshop. The three studies within this dissertation examine issues of equity including student empowerment and gender issues across these courses. The voice of students in a studio physics class of introductory electro- magnetism was sought out using an action research approach, with data including surveys, notes from one-on-one student/teaching assistant conferences, and counts of interactions with instructors. Learning in an Astro 101 course was investigated via both quantitative and qualitative data, with quantitative data consisting of pre/post-test results broken down by astronomy content and dataset skills, and by cognitive load level, showing that female students struggled to demonstrate improvement in their understanding. This was supported by qualitative data including notes while students were working on the activity, transcriptions of video and audio recordings, and interviews. And the discourse was analyzed to search for the positioning and interactions with a group of five mixed-sex in-service primary and secondary STEM teachers during an astronomy professional development workshop. These teachers used their words, body language, and the computer to position themselves as supporting a hierarchy based on gender and experience. They also showed evidence of both sensemaking and "playing the classroom game". Challenges to empowering learners in an equitable fashion were found across all three participant populations, as well as in the researchers themselves. This dissertation shows the need for more work to equitably reach all learners within post-secondary physics departments, including STEM majors, non-STEM majors, and K-12 teachers, and the need to address gendered dynamics in the classroom or PD environment. Recommendations are made of teaching approaches that show promise for reducing sources of inequity in classroom dynamics. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]