The overhead projector is perhaps passing out of use, but it is still a useful device with which to do lecture demonstrations. In my early years at Kenyon I was teaching the pre-med course, and found that the overhead projector was an ideal platform for showing the phenomena of polarized light. This note is a discussion of how I learned to use the…

Almost everyone "knows" that steam is visible. After all, one can see the cloud of white issuing from the spout of a boiling tea kettle. In reality, steam is the gaseous phase of water and is invisible. What you see is light scattered from the tiny droplets of water that are the result of the condensation of the steam as its temperature…

The familiar kaleidoscope toy was developed by the Scottish physicist David Brewster (1781-1868) in 1816, patented by him in 1817, and described in his 1819 book, "A Treatise on the Kaleidoscope." Generations of elementary students have made their own kaleidoscopes by assembling three microscope slides inside a tube and looking through it at a…

One of the rewards of walking up the scores of steps winding around the inside of the shaft of a lighthouse is turning inward and examining the glass optical system. This arrangement of prisms, lenses, and reflectors is used to project the light from a relatively small source in a beam that can be seen far at sea.

Here is a quick way to measure the index of refraction of water using the phenomenon of total internal reflection.

Discusses and provides an example of reflectivity approximation to determine whether reflection will occur. Provides a method to show thin-film interference on a projection screen. Also applies the reflectivity concepts to electromagnetic wave systems. (MVL)

Discusses the production of hundreds of pinhole images of a recent eclipse of the sun through the leaf canopy. Provides photograph of the images. (MVL)

Describes an hour-long activity to illustrate the properties and use of cylindrical concave mirrors. Appropriate for non-science majors or high school students. (WRM)

Discusses how the caustic by reflection is formed. Indicates that the phenomenon can be demonstrated by showing the reflection of the light from a distant point source from the inner curve of a polished hoop of metal (such as a wedding ring). (JN)

Describes the construction and use of a set of "relativistic metersticks" that represent the apparent lengths of a meterstick passing a stationary observer at relative speed v/c. (WRM)

Describes ray tracing techniques and the method of virtual mirrors to locate images when using multiple mirrors. (JN)

Describes method for locating images in simple and complex systems of thin lenses and spherical mirrors. The method helps students to understand differences between real and virtual images. It is helpful in discussing the human eye and the correction of imperfect vision by the use of glasses. (Author/SK)

Describes several methods of executing lecture demonstrations involving the recombination of the spectrum. Groups the techniques into two general classes: bringing selected portions of the spectrum together using lenses or mirrors and blurring the colors by rapid movement or foreshortening. (JM)