Presentations

Radiometer

Detection of IR radiation from hair dryer and/or special IR source.

What it Shows:

Detection of infra-red radiation by the rotation of a paddle-wheel vane inside a low pressure flask.

How it Works:

A radiometer consists of a partially evacuated flask containing a four bladed vane (see figure 1). One side of each blade is a matt black, the other silver. The black surface, being a better absorber and radiator of heat, warms the air above its surface more than the silver. The resulting higher kinetic energy of these air...

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Florence's Rainbow

What it shows:

A beam of white light incident on a giant raindrop (simulated by a water-filled round flask) produces a full rainbow of colors. As with real rainbows, one can also see that the light intensity inside the rainbow is much greater than outside the rainbow.

How it works:

A Florence (round-bottomed) flask is completely filled with water and sealed with a rubber stopper. A Beseler slide projector 1 serves as the sunlight. The light incident on the giant raindrop is refracted, reflected, and refracted once more, back in the direction of the...

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Single Photon Interference

Wave/particle duality observed in Young's double slit experiment with camera sensitive to individual photons.

What it shows:
In this demonstration we perform the double-slit interference experiment with extremely dim light and show that even when the light intensity is reduced down to several photons/sec, the audience can see the familiar Young's double-slit interference pattern build up over a period of time. This addresses the question of how can single photons interfere with photons that have already gone through the apparatus in the past, or with those that...

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Periodic Potential

What it shows:

Ball bearings simulate atoms in a lattice sitting at local potential minimums. Giving them energy excites the atoms and they oscillate about their equilibrium positions in these wells; only with large amounts of energy can they be truly dislocated.

How it works:

A piece of wood 100 × 25 × 2cm acts as the ‘potential’ structure of the lattice. The atoms, 3cm diameter ball bearings sit at the bottom of a cosine varying potential cut to about 10cm depth in the wood by a jig saw.The balls are held in the 2-dimensional...

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Solid, Liquid, Gaseous CO2

Observation of phase changes with corresponding pressure changes.

A two ml. plastic microcentrifuge vial and a small shop vise are used together to melt dry ice.

Wear safety glasses for this demo. The vial can explode, or shoot out of the vice, from the pressure of liquid carbon dioxide. Set up a camera with a close shot of an empty vial before putting in a loaded vial.

Crush a pellet of dry ice to make pieces that fit into the vial. Place a couple of pieces in the vial, and snap the lid closed.

Immediately place the vial horizontally in the jaws of the vice,...

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Jumping Ring

Shoot the ring through the roof after dipping it in liquid N2; Lenz's law induced EMF in metal ring.

What it shows: 

The induced current in a metal ring is dramatically increased by lowering the ring's temperature.

How it works: 

Here is an extension of the ...

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Armillary Sphere

Model to show celestial sphere; larger version has capacity to show lunar motions.

What it shows:

The position and motions of heavenly bodies are projected against a hypothetical sphere of infinite radius, centered on the Earth, called the Celestial Sphere. With this demo you can explain the motions of the stars and of the Sun, and show various aspects of the seasons.

How it works:

The main features of the sphere itself are shown schematically in figure 1. The spherical wire cage defines the celestial sphere, its...

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Samples of Elements

First day of Gen Chem: Metals and non-metals; solids, liquid and gas elements; compound of elements.

Copper, sulfur, lead, iron, antimony, iodine, carbon as powder and graphite sample, mercury, copper iodate, oxygen balloon.

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