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Optics I

4. Lenses

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The fourth mini-lecture discusses the lens, focusing in particular on: (i) the history of the lens, including developments made by Arabic scientist Ibn Sahl, lenses as glasses and glasses in art, and the optical pioneer, Augustin-Jean Fresnel, who improved the lens in the 17th century and made it easier to use in lighthouses; (ii) how a lens can focus collimated light to a point; (iii) the power P of a lens, which is given by 1/f, where f is the focal length of the lens; (iv) how lenses are extremely useful for opticians and those who wear glasses; (v) the relationship between focal length and the radius of curvature of a lens; (vi) types of lenses such as plano-convex, plano-concave, bi-convex, bi-concave, and meniscus, as well as the general formula for optical power of a lens; and (vii) two exercises on lenses.


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 - Lenses [Video]. MASSOLIT.

MLA style

Adams, Charles. "Optics I – Lenses." MASSOLIT, uploaded by MASSOLIT, 12 Jan 2022,

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