# Harvard Natural Sciences Lecture Demonstrations ## Paraxial Ray Optics Cloaking A new optical illusion has been added to our geometric optics repertoire: A combination of four converging lenses creates a 3D c [ Read more arrow\_circle\_right ](/presentations/paraxial-ray-optics-cloaking) ![wolfface-1024x683.jpg](/sites/g/files/omnuum7861/files/styles/hwp_21_9__1920x825/public/science-demonstrations/files/wolfface-1024x683.jpg?h=797b6157&itok=eRXf_y1N) ## expand\_more ## **About the Catalog** This website is an ongoing project to create a comprehensive library of physics demonstrations, simulations, videos, and other useful resources available at the Harvard Science Center. Having evolved from "The Demonstrative Physicist's Companion," a handbook begun in 1990 by W. Rueckner and S. Steel, this website goes far beyond a compilation of all the demonstrations in our current repertoire. Included in the table of contents at the left are twelve topic sections relating to particular areas of physics, chemistry, and math. Each topic section is further divided into sub-sections in which the demonstrations are listed. You may find browsing through these sections helpful to get ideas for your lecture, but even more helpful is the ability to **search the catalog with key words** so that you needn't rely on our categorization or cross-referencing schemes to find what fits your needs. It is our intention to make this site as useful as possible. Any suggestions from you, the user, are greatly appreciated. If you found a demonstration listed for which you wished there was an "in-depth" description, let us know. You can contact us by the various methods listed above. ## **Key to Catalog Listings** **Size**: from small \[S\] (benchtop) to extra large \[XL\] (most of the hall) **Setup Time**: <10 min \[t\], 10-15 min \[t+\], >15 min \[t++\] /span> **Rating**: from good \[★\] to wow! \[★★★★\] or not rated \[—\] [Complete key to listings](/key-catalog-listings "Key to Catalog Listings") ## Mission Statement We provide visual demonstrations for a wide variety of topics to supplement lectures in physics, chemistry, astronomy, and biology. Our lecture demonstrations have two important purposes: to increase student understanding of the concepts demonstrated, and to increase student enjoyment of class. Natural Science Lecture Demonstrations consists of a team of physicists and chemists who develop, construct, and present demonstrations for lectures in the Science Center building. Working with members of faculty and testing our skills in machining, electronics, and dazzling imagery, we aim to clarify and enhance the scientific concepts presented in lecture with visible, memorable, and sometimes mind-blowing effects. ## What's New Download 6 citations download- [BibTeX](/bibcite/export?pager_style=no_pager&number_of_items=6&sort_field=bibcite_year--desc&&content_filter%5B0%5D=335026&content_filter%5B1%5D=381716&content_filter%5B2%5D=381726&content_filter%5B3%5D=426066&content_filter%5B4%5D=434961&content_filter%5B5%5D=436876&content_filter%5B6%5D=437166&content_filter%5B7%5D=437171&content_filter%5B8%5D=439931&content_filter%5B9%5D=440021&content_filter%5B10%5D=440171&content_filter%5B11%5D=440271&content_filter%5B12%5D=440391&content_filter%5B13%5D=446386&content_filter%5B14%5D=446441&content_filter%5B15%5D=495731&content_filter%5B16%5D=496461&&format=bibtex) - [EndNote X3 XML](/bibcite/export?pager_style=no_pager&number_of_items=6&sort_field=bibcite_year--desc&&content_filter%5B0%5D=335026&content_filter%5B1%5D=381716&content_filter%5B2%5D=381726&content_filter%5B3%5D=426066&content_filter%5B4%5D=434961&content_filter%5B5%5D=436876&content_filter%5B6%5D=437166&content_filter%5B7%5D=437171&content_filter%5B8%5D=439931&content_filter%5B9%5D=440021&content_filter%5B10%5D=440171&content_filter%5B11%5D=440271&content_filter%5B12%5D=440391&content_filter%5B13%5D=446386&content_filter%5B14%5D=446441&content_filter%5B15%5D=495731&content_filter%5B16%5D=496461&&format=endnote8) - [EndNote 7 XML](/bibcite/export?pager_style=no_pager&number_of_items=6&sort_field=bibcite_year--desc&&content_filter%5B0%5D=335026&content_filter%5B1%5D=381716&content_filter%5B2%5D=381726&content_filter%5B3%5D=426066&content_filter%5B4%5D=434961&content_filter%5B5%5D=436876&content_filter%5B6%5D=437166&content_filter%5B7%5D=437171&content_filter%5B8%5D=439931&content_filter%5B9%5D=440021&content_filter%5B10%5D=440171&content_filter%5B11%5D=440271&content_filter%5B12%5D=440391&content_filter%5B13%5D=446386&content_filter%5B14%5D=446441&content_filter%5B15%5D=495731&content_filter%5B16%5D=496461&&format=endnote7) - [Endnote tagged](/bibcite/export?pager_style=no_pager&number_of_items=6&sort_field=bibcite_year--desc&&content_filter%5B0%5D=335026&content_filter%5B1%5D=381716&content_filter%5B2%5D=381726&content_filter%5B3%5D=426066&content_filter%5B4%5D=434961&content_filter%5B5%5D=436876&content_filter%5B6%5D=437166&content_filter%5B7%5D=437171&content_filter%5B8%5D=439931&content_filter%5B9%5D=440021&content_filter%5B10%5D=440171&content_filter%5B11%5D=440271&content_filter%5B12%5D=440391&content_filter%5B13%5D=446386&content_filter%5B14%5D=446441&content_filter%5B15%5D=495731&content_filter%5B16%5D=496461&&format=tagged) - [Marc](/bibcite/export?pager_style=no_pager&number_of_items=6&sort_field=bibcite_year--desc&&content_filter%5B0%5D=335026&content_filter%5B1%5D=381716&content_filter%5B2%5D=381726&content_filter%5B3%5D=426066&content_filter%5B4%5D=434961&content_filter%5B5%5D=436876&content_filter%5B6%5D=437166&content_filter%5B7%5D=437171&content_filter%5B8%5D=439931&content_filter%5B9%5D=440021&content_filter%5B10%5D=440171&content_filter%5B11%5D=440271&content_filter%5B12%5D=440391&content_filter%5B13%5D=446386&content_filter%5B14%5D=446441&content_filter%5B15%5D=495731&content_filter%5B16%5D=496461&&format=marc) - [PubMedId](/bibcite/export?pager_style=no_pager&number_of_items=6&sort_field=bibcite_year--desc&&content_filter%5B0%5D=335026&content_filter%5B1%5D=381716&content_filter%5B2%5D=381726&content_filter%5B3%5D=426066&content_filter%5B4%5D=434961&content_filter%5B5%5D=436876&content_filter%5B6%5D=437166&content_filter%5B7%5D=437171&content_filter%5B8%5D=439931&content_filter%5B9%5D=440021&content_filter%5B10%5D=440171&content_filter%5B11%5D=440271&content_filter%5B12%5D=440391&content_filter%5B13%5D=446386&content_filter%5B14%5D=446441&content_filter%5B15%5D=495731&content_filter%5B16%5D=496461&&format=pubmed_id) - [RIS](/bibcite/export?pager_style=no_pager&number_of_items=6&sort_field=bibcite_year--desc&&content_filter%5B0%5D=335026&content_filter%5B1%5D=381716&content_filter%5B2%5D=381726&content_filter%5B3%5D=426066&content_filter%5B4%5D=434961&content_filter%5B5%5D=436876&content_filter%5B6%5D=437166&content_filter%5B7%5D=437171&content_filter%5B8%5D=439931&content_filter%5B9%5D=440021&content_filter%5B10%5D=440171&content_filter%5B11%5D=440271&content_filter%5B12%5D=440391&content_filter%5B13%5D=446386&content_filter%5B14%5D=446441&content_filter%5B15%5D=495731&content_filter%5B16%5D=496461&&format=ris) [Locked Brakes](/presentations/locked-brakes). [Locked Brakes](/presentations/locked-brakes). - add\_circle do\_not\_disturb\_on Abstract The difference between static and kinetic friction can cause the car to skid when braking. ### **What it shows:** The automobile is a radio-contolled car (the same one we use for the *Reactionary* *Roadbed*). When the front wheels are locked so that they can't turn... [Vacuum Cannon](/presentations/vacuum-cannon). [Vacuum Cannon](/presentations/vacuum-cannon). - add\_circle do\_not\_disturb\_on Abstract If you're feeling pressure to do something fun, consider the vacuum cannon... See slow-motion footage of the Vacuum Cannon in action () ### What it Shows Air rushing into an evacuated tube pushes a ping-pong ball down the... [Rope Friction Around Pole](/presentations/rope-friction-around-pole). [Rope Friction Around Pole](/presentations/rope-friction-around-pole). - add\_circle do\_not\_disturb\_on Abstract The tension force in a rope grows exponentially with the number of turns the rope makes around a pole. ### What it shows: Many people have probably observed that, by wrapping a rope around a post, a person can hold in check a much larger force than would... [Sound Reflections in Pipes](/presentations/sound-reflections-pipes). [Sound Reflections in Pipes](/presentations/sound-reflections-pipes). - add\_circle do\_not\_disturb\_on Abstract A pulse of sound gets "inverted" when reflecting off the open end of a pipe, but does not get inverted when reflecting off the closed end. ### What It Shows Due to an impedance mismatch, a sound pressure pulse traveling down the length of a pipe suffers a... [Paraxial Ray Optics Cloaking](/presentations/paraxial-ray-optics-cloaking). [Paraxial Ray Optics Cloaking](/presentations/paraxial-ray-optics-cloaking). - add\_circle do\_not\_disturb\_on Abstract A new optical illusion has been added to our geometric optics repertoire: A combination of four converging lenses creates a 3D cloaking effect. ### What it shows The demonstration is a replica of an experiment described by J.S. Choi and J.C. Howell (Univ of... [Vortex Shedding in Water](/presentations/vortex-shedding). [Vortex Shedding in Water](/presentations/vortex-shedding). - add\_circle do\_not\_disturb\_on Abstract Water moving around a cylindrical pendulum makes the cylinder swing at the vortex shedding frequency. ### What it Shows: When fluid flows around a cylindrical object, there is a range of flow velocities for which a von Karman vortex street is formed. The... [ More arrow\_circle\_right ](/presentations)