[XL | t++ | ***]  inverse square law, luminosity

What it shows:  The intensity of light from a point source decreases as 1/r², where r is the distance from the source.

How it works:  For the point light source, we use a 1500 watt clear light bulb. The detector is a small solar panel.¹ The output current is directly proportional to the intensity of the light falling on the panel and the current is displayed on an analog milliameter. (The current can also be measured by a digital meter or computer.) Measured...

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What it shows:

Hero's Principle states that light undergoing a reflection from a plane surface will follow the path of least distance. Here is a mechanical analog showing that when the angle of incidence equals the angle of reflection, the path length is minimized.

How it works:

The light path is represented by a 2m length of nylon rope that runs from a fixed end, 'reflects' around a pulley, back up to a second pulley (figure 1). The surplus rope is held taught by a 1kg mass. The pulleys, 6cm in diameter are free to move...

What it shows:

The simplest method of controlling light to form an image is to use an opaque mask with a pinhole in it. Rectilinear propagation of light explains all (nearly). A video camera is substituted for the old prototypal shoe box so that an entire audience can see the pinhole image "live."

How it works:

An extremely light-sensitive video camera ¹ sans lens substitutes for the pinhole camera box and film. The front of the Newvicon is the image plane and, as this sits right behind the faceplate of the camera...

What it shows:

All of the concepts summarized by the above keywords can be clearly and quantitatively demonstrated with this piece of apparatus.

How it works:

A light source ¹ rotates around the circumference of a large white disk ² with degree graduations around the entire perimeter. The collimated beam of light grazes the surface of the disk, creating a highly visible pencil of light, so that ray tracing is easily accomplished. A horizontal mirror, positioned at the center of the disk, is used for the law of...

What it shows:

With an assortment of plane and curved mirrors, convex and concave lenses, parallel-sided block and prisms, the Klinger ¹ Blackboard Optics Kit© allows one to demonstrate all the classic examples in geometric optics by actual ray tracing in two dimensions.

How it works:

All components in the kit are magnetically attached to the blackboard. The light source produces a grazing pencil of light on the surface of the board which may be refracted through, or reflected from, the various optical components. Single...