6A60.10 - Thin Lenses - Blackboard Optics

Code Number:
Demo Title:
Thin Lenses - Blackboard Optics
Geometric Optics
Area of Study:
Blackboard Optics Unit, Concave and Convex Lens Sets, and Long Focal Length Convex Lens Set.

Video Credit: Jonathan M. Sullivan-Wood

Make sure the five rays coming out of the projector are parallel. Place a plano-convex or plano-concave lens with the middle ray going through the center of the lens. Accessories are available so that you can do a double convex or double concave lens if desired. The focal point may not be exact, but will be close enough for people to get the idea.

  • Yu Jin, Hee Ra Kiim, Yu Chen, Ji Hyun Kim, Hyukjoon Choi, Jung Bog Kim, "Variable Focal Length lenses Made of Gelatin", TPT, Vol. 61, #6, Sept. 2023, p. 470.
  • "Erratum: "Geometric Optical Experiments Using Water Mixed With Highlighter Ink", Phys. Teach. 60, 765-767", TPT, Vol. 61, #6, Sept. 2023, p. 427.
  • Yu Chen, Hee Ra Kim, Yu Jin Ahn, Jung Bog Kim, "Geometric Optical Experiments Using Water Mixed with Highlighter Ink", TPT, Vol. 60, #9, Dec. 2022, p. 765.
  • Shih-Hsin Ma, Jun-Yi Wu, Chun-Ming Chiang, "Drawing the Light Paths at a Lens to Find the Effective Focal Lengeh and Principal Planes", TPT, Vol. 60, #7, Oct. 2022, p. 591.
  • Nuri Balta, "Gaussian Formula for Ray Tracing in Lenses and Mirrors", TPT, Vol. 60, #1, Jan. 2022, p. 56.
  • Chris Chiaverina, "Gelatin Optics Revisited", TPT, Vol. 59, #5, May 2021, p. 380.
  • Lasse Heikkinen, Antti Savinainen, and Markku Saarelainen, "Virtual Ray Tracing as a Conceptual Tool for Image Formation in Mirrors and Lenses", TPT, Vol. 54, #9, Dec. 2016, p. 538.
  • Jeff Marx and Shabbir Mian, "Using Nonprinciple Rays to Form Images in Geometrical Optics", TPT, Vol. 53, #8, Nov. 2015, p. 497.
  • Mickey Kutzner, "The Laser Level as an Optics Laboratory Tool", TPT, Vol. 51, #9, Dec. 2013, p. 532.
  • Decha Suppapittayaporn, Bhinyo Panijpan, and Narumon Emarat, "Can We Trace Arbitrary Rays To Locate an Image Formed by a Thin Lens?", TPT, Vol. 48, #4, Apr. 2010, p. 256.
  • Gene Mosca, "Alternative Presentation", TPT, Vol. 47, #6, Sept. 2009, p. 327.
  • Paul Gluck and Benjamin Perkalskis, "Analog of Optical Elements for Sound Waves in Air", TPT, Vol. 47, #1, Jan. 2009, p. 75.
  • Matthew Craig, Ryan Johnson, and Sara Schultz, "Steamy Optics: A System for Demonstrating Geometric and Physical Optics", TPT, Vol. 45, #4, Apr. 2007, p. 247.
  • F. Logiurato, L. M. Gratton, and S. Oss, "Making Light Rays Visible in 3-D", TPT, Vol. 45, #1, Jan. 2007, p. 46.
  • Edward P. Wyrembeck, "Modeling the Behavior of Light with a Light Cone", TPT, Vol. 44, #8, Nov. 2006, p. 549.
  • Mario Branca and Isabella Soletta, "Construction of Optical Elements with Gelatin", TPT, Vol. 41, #4, Apr. 2003, p. 249.
  • Ponn Maheswaranathan, "Revisiting Visualizing the Thin-Lens Formula", TPT, Vol. 39, #8, Nov. 2001, p. 452.
  • Soumya Chakravarti and P.B. Siegel, "Visualizing the Thin-Lens Formula", TPT, Vol. 39, #6, Sept. 2001, p. 342.
  • David L. Wagner and Thomas A. Walkiewicz, "When The Eye Meets The Lens", TPT, Vol. 38, #8, Nov. 2000, p. 474.
  • Robert W. Lawrence, "Magnification Ratio and the Lens Equations", TPT, Vol. 38, #3, Mar. 2000, p. 170.
  • Scott C. Dudley, "Trick of the Trade - How to Quickly Estimate the Focal Length of a Diverging Lens", TPT, Vol. 37, #2, Feb. 1999, p. 94.
  • Joseph Ganem, "A Behavioral Demonstration of Fermat's Principle", TPT, Vol.  36, #2, Feb. 1998, p. 76.
  • Patyick Bunton , "Edible Optics: Using Gelatin to Demonstrate Properties of Light", TPT, Vol. 35, #7, Oct. 1997, p. 421.
  • Heidi Strahm Black, "More on Eating Optics", TPT, Vol. 36, #2, Feb. 1997, p. 67.
  • W. Steve Quon, "Matrix Treatment of Ray Optics", TPT, Vol. 34, #6, Sept. 1996, p. 378.
  • H. E. Siefken and H. E. Tomaschke, "Equipment for an Inexpensive Introductory Optics Lab", TPT, Vol. 32, #5, May 1994, p. 315.
  • Ludwik Kowalski, "On Field Lenses", TPT, Vol. 30, #6, Sept. 1992, p. 366.
  • R.H. Stinson, "A Biconvex Diverging Lens", TPT, Vol. 29, #9, Dec. 1991, p. 592.
  • Harry D. Downing, Walter L. Trikosko, and Paula Lovell, "Ray Tracing for a Few $", TPT, Vol. 29, #6, June 1991, p. 369.
  • Stuart Leinoff, "Ray Tracing with Virtual Objects", TPT, Vol. 29, #5, May 1991, p. 275.
  • Roger E. Malcolm, "Fluid Lenses", TPT, Vol. 27, #8, Nov. 1989, p. 636.
  • Se-yuen Mak, "A Simple Method to Determine the Refractive Index of Glass", TPT, Vol. 26, #8, Nov. 1988, p. 526.
  • Robert Krohl, "A Convex Lens as a Thick Mirror", TPT, Vol. 26, #1, Jan, 1988, p. 18.
  • John F. Koser, "A Laboratory Activity in Geometric Optics Using a 35-mm Single Lens Reflex Camera", TPT, Vol. 25, #7, Oct. 1987, p. 428.
  • David Bardell, "The First Practical Application of Optical Magnification", TPT, Vol. 24, #4, Apr. 1986, p. 202.
  • Ralph B. Knollenberg, "Ray Optics Corridor Demonstration", TPT, Vol. 19, #8, Nov. 1981, p. 563.
  • J. Gerald Anderson, "A Practical Analysis of the Magnifying Glass", TPT, Vol. 19, #6, Sept. 1981, p. 417.
  • Thomas B. Greenslade Jr. and Franklin Miller, Jr., "The Method of Curvatures", TPT, Vol. 19, #2, Feb. 1981, p. 88.
  • Robert Gardner, "Ray Models of Concave Mirrors and Convex Lenses", TPT, Vol. 18, #8, Nov. 1980, p. 608.
  • Pierre Lucie, "Thin Lenses Formulas", TPT, Vol. 16, #8, Nov. 1978, p. 555.
  • Robert L. Siddon, "Simple Derivation of the Lens Maker's Equation", TPT, Vol. 16, #9, Dec. 1978, p. 647.
  • Duncan T. Moore and Danette P. Ryan, "Gradient Index Optical Lenses", TPT, Vol. 15, #7, Oct. 1977, p. 409.
  • George L. Hazelton and Larry Strooud, "Three Dimensional Ray Tracing", TPT, Vol. 10, #6, Sept. 1972, p. 344.
  • Ian R. Gatland, "Thin Lens Ray Tracing", AJP, Vol. 70, #12, Dec. 2002, p. 1184.
  • Og-7, 9, 10: Freier and Anderson,  A Demonstration Handbook for Physics.
  • O-310: "Blackboard Optics", DICK and RAE Physics Demo Notebook.
  • George M. Hopkins, "Lenses", Experimental Science, p. 204.
  • Pat Murphy, Ellen Macaulay, and the staff of the Exploratorium, "Lens Experiments", Exploratopia, p. 290.
  • Roger E. Malcom, Edited by Karl Mamola, "Fluid Lenses", Apparatus for Teaching Physics, p. 222.
  • Janice VanCleave, "Determine How the Focal Length of a Magnifying Lens Affects Its Magnifying Power", Super Science Challenges, p. 19.
  • Raymond Bruman, "Optical Bench", Exploratorium Cookbook I, p. 12.1 - 12.3.
  • Stangl, "Concave & Convex Lenses", Science Toolbox.
  • C. Harvey Palmer, "Experiment A1: Thin Lenses and Thin Lens Combinations", Optics - Experiments and Demonstrations, John Hopkins Press, 1962.
  • "Reflection and Refraction", Selective Experiments in Physics, CENCO, 1962.
  • "Refraction Through a Single Thin Lens", Selective Experiments in Physics, CENCO, 1962.
  • "Nodal Slide:  A Study of the Properties of Thick Lenses", Selective Experiments in Physics, CENCO, 1962.

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