As visitors approach the Haunted Physics Laboratory, they are greeted by a larger-than-life photo of Albert Einstein and an invitation to "come in for a spell." They hear music emanating from inside ("Phantom of the Opera," for example). After picking up a copy of the Haunted Laboratory Guide, they bravely enter.²

One of the exhibits that visitors encounter inside is the "Ghostly Light," which most readers would recognize as a standard spherical mirror demonstration, dressed up for Halloween. A working flicker-type light bulb is hidden in a black box, upside down, directly below an empty light socket located on top of the box. The box, open on the side facing the mirror, is precisely aligned in the region of the mirror's center of curvature so that a real image of the light bulb is formed above the empty socket. Partitions are arranged to restrict the vantage-point of approaching visitors. As they come closer and walk around to the side of the setup, the light bulb disappears. Here's what the Haunted Laboratory Guide says about this exhibit:

Ghostly Light

The light bulb you see is an image formed by a concave mirror.

— Is the image real or virtual? (Real images formed by a single mirror appear in front of the mirror. Virtual images formed by a single mirror appear behind the mirror.)

— To check your answer, hold a sheet of paper upright at the site of the image. If the image is real, you should see it on the paper. Do you see it?

— Where is the real light bulb located?

— You should be able to find a ray diagram nearby that explains the setup.

Moving on, the haunted lab would hardly be complete without some frightful electrical devices. For example, visitors ponder what causes the climbing spark to rise as they eye the DANGER! HIGH VOLTAGE sign of "Jacob's Ladder," and they have a truly "Shocking Experience" learning how to bring a dead bat back to life³ using a Van de Graaff generator (Fig. 1).

Figure 1.

A surprisingly popular exhibit asks visitors to "Conjure Up a Ghost or Two" at an optical bench. The object for image formation is an illuminated picture of a ghost. Here's what the laboratory guide says:

Conjure Up a Ghost or Two

— There are two positions of the convex lens that produce a sharp image of the ghost on the screen. One position produces a diminished (small)image. The other position produces a magnified (large) image. Can you find them? Hint: The large image occurs when the lens is somewhere far from the screen. The small image occurs when the lens is much closer to the screen.

— Are the images real or virtual? Are they upright or inverted?

— The same convex lens can produce yet a third image. This one is not on the screen. Can you find it? Is it real or virtual? Is it upright or inverted?

An exhibit called "Wizard's Wand Power" makes good use of an antique demonstration meter and a bar magnet painted black with white tips to look like a magic wand. The Haunted Laboratory Guide says:

Wizard's Wand Power

This demonstrates electromagnetic induction, a discovery by "electrical wizard" Michael Faraday in 1831. Commercial power plants use Faraday's discovery to generate ac (alternating current) electricity.

— Move the wand (actually a permanent magnet) back and forth inside the coil of wire. Time the back and forth movement to match the swing rate of the needle. The meter measures the resulting electrical current induced in the circuit. Some of the work you do to produce relative motion between the magnetic field of the magnet and the coil of wire is converted to electrical energy.

— What can this equipment be used to demonstrate?

(a) Law of induction

(b) Conversion of energy from mechanical to electrical

(c) Resonance

(d) Relativity

(e) All of the above.

Can you explain why the answer is (e)?

As they continue to work their way through the lab, visitors soon discover that the haunting music they have been hearing comes from exhibits that encourage them to "Create a Laser Light Show" (using lasers and diffraction gratings) and enjoy "Seeing Music with a Color Organ."⁴

There are mechanical exhibits in the haunted lab as well. "Apple Acrobatics" is an all-time favorite (Fig. 2). Two apples suspended from strings and linked by a rubber band can be made to stop on command. Knowing that the apples' energy is transferred back and forth allows the operator to predict when each apple will stop. It's a beautiful illustration of one of the driving motivations of science: to learn how things behave in order to be able to predict future behavior. The laboratory guide says:

Apple Acrobatics

The two apple pendulums are coupled to each other by a rubber band. The pendulums should have the same length.

— Start one apple swinging while holding the second one stationary. Then let the second one go and observe what happens. The efficient transfer of energy back and forth between the two pendulums is a phenomenon called resonance or "sympathetic vibration."

— Resonance only occurs if the pendulums are "in tune "with each other. To be in tune requires that they have the same length and therefore the same natural frequency of oscillation. How would you test this requirement?

Figure 2.

After interacting with these and some 21 other exhibits, it is time now to meet "The Department Head" located in an adjoining room. A box sits on what appears to be a three-legged table. When a door in the front of the box suddenly opens, a live head is seen inside. It talks to the visitors. A glance beneath the table confirms that the body is missing (Fig. 3). "The Department Head" is a recreation of the so-called Sphinx Illusion invented in 1865 by Thomas Tobin, a science lecturer at the Royal Polytechnic Institution.⁵ Two plane mirrors are placed between the legs of the three-legged table to hide the person's body (Fig. 4). When properly arranged, the mirrors reflect light from side curtains to form virtual images that coincide with the back curtain. In Fig. 4 the bottom edges of the mirrors can be seen. However, when the shag carpet is fluffed up to hide the edges of the mirrors and the lights are dimmed, the illusion is stunning. Viewed from the front it appears as though there is nothing under the table.⁶ The expression "it's all done with mirrors" is largely due to this and other mirror illusions invented for stage magicians by Tobin.

Figure 3.

Figure 4.

The photos and the brief descriptions given above provide only a small sampling of the 30 exhibits in the Haunted Physics Lab at Creighton University. Detailed information about all of the exhibits is available on a DVD. The video takes viewers on an exhibit-by-exhibit tour while the lab is in session. Another tour, with the room lights turned on, clearly shows the setups and the equipment used at each station. Clips of television news coverage are also included.

To receive a copy of the DVD and the Haunted Laboratory Guide, see Ref. 2 at the end of this paper.