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Optics I

3. Refraction and Reflection

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In this mini-lecture, we delve deeper into the concepts of refraction and reflection. In particular, we consider: (i) refraction as the bending of light at the interface between two optical mediums; (ii) the index of refraction n of various optical mediums, such as air, glass, and water, that characterises how much light bends when entering that medium; (iii) a comparison between rays and waves, including parallel, converging, and diverging rays; (iv) the change in speed and wavelength of a light wave when it enters a new optical medium; (iv) the ray simulator (Rick Tu, Ray Optics Simulation, 2021) as a hands-on approach to understanding refraction; (v) another interactive simulator (Physics Education Technology, University of Colorado, Bending Light Simulation, 2021) that illustrates the bending of white light in a prism; (vi) total internal reflection; and (vii) three exercises on refraction, refection, total internal reflection, and dispersion.


In this course Professor Charles Adams (Durham University) gives an introduction to optics for GCSE students. In the first mini-lecture, we explore the big picture of optics, defining it broadly as the science of light, seeking to understand light as a wave, and concluding with some impacts and applications of optics. In the second mini-lecture, we explore the concept of light rays, their historical developments dating back to the tenth century, and some of their properties such as refraction, reflection, and absorption. In the third mini-lecture, we delve deeper into refraction and reflection as we introduce the concept of the index of refraction of optical mediums, look at examples, and play around with some simulators to mimic these effects. The fourth mini-lecture turns towards lenses, including important historical developments, how a lens works, and the power of a lens. The fifth mini-lecture explores imaging, addressing the question of how to make a better lens, the limitations of the lens, and how our improved understanding of optics and lenses led to advances in areas such as microscopy and medicine.


Charles Adams is a Professor in the Department of Physics at Durham University. His principal research interests are in experimental quantum optics, in particular light-matter interactions in strongly-interacting atomic systems. He was the 2014 recipient of the Joseph Thomson Medal, awarded by the Institute of Physics (IOP) to those who have made distinguished contributions to atomic or molecular physics. In 2020, he was awarded the Holweck Prize by the French Physical Society and the IOP for pioneering work in quantum optics. Professor Adams is also a co-author of the optics textbook Optics f2f: From Fourier to Fresnel (2018).

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APA style

Adams, C. (2022, January 12). Optics I - Refraction and Reflection [Video]. MASSOLIT.

MLA style

Adams, Charles. "Optics I – Refraction and Reflection." MASSOLIT, uploaded by MASSOLIT, 12 Jan 2022,

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