Presentations

Resonant Fountain Tube

Standing sound waves in a glass pipe are made evident by the fountains of kerosene inside the pipe.

What it shows:

The air inside a very large glass pipe (partially filled with a fluid) is acoustically excited into a standing wave. Once resonating, the locations of the velocity antinodes inside the pipe are dramatically made evident by the vigorous agitation of the fluid, resulting in fabulous foaming frothing fountains of fluid. The velocity of sound can also be determined by noting the resonance frequency and measuring the distance between antinodes....

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Siren Discs

What it shows:

Demonstrate musical intervals, the relation of pitch to frequency, and autocorrelation in psycho-acoustics.

How it works:

A 25 cm diameter metal disk has a number of concentric rows of regularly spaced holes. When rotated at a uniform speed while blowing air at a row of holes, a musical note is produced by the sequence of regular puffs of air issuing from successive holes. The frequency is determined by the speed of rotation and the known number of holes.

The numbers of holes in the successive rows are 24, 27...

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Walk-In Faraday Cage

What it shows:

A lecturer's faith in the principle that an electric field cannot exist inside a charged conductor is put to the test using a Faraday cage that is large enough to sit in.

How it works:

The lecturer (or some volunteer) climbs the three steps and sits upon a plain wooden chair. Their assistant pulls the mesh door closed and fastens it. A Van de Graaff, whose dome is in contact with the cage, begins to charge itself and the cage up to a high voltage. The person inside is oblivious to the large amount of charge now...

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TV Image Deflection

Image on black and white television is deflected by a magnet, not unlike the Maltese Cross.

What it shows:
The television is basically a sophisticated cathode ray tube. The electron beam in the TV is influenced by magnetic fields in the same way as in Crookes tubes.

How it works:
The image on a black & white TV is formed by a single electron gun scanning the screen. Holding a strong magnet to the side or in front of the screen deflects the beam from its regular sweep pattern, distorting the image.

Setting...

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Eddy Currents at LN2 Temperature

What it shows:

A rectangular block of copper (measuring 6"×6"×2"), offers VERY little resistance to eddy currents generated by dragging a magnet across its surface. Thus the Lorentz force between the eddy currents and magnetic field is quite strong and you can feel a sizable drag force. Dropping a magnet onto the surface likewise produces a sizable Lorentz force, as evidenced by the damped motion of the magnet's fall. The effects are quite dramatic at liquid nitrogen temperature.

How it works:

Copper has a positive temperature...

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OHP RLC Circuit

What It Shows

The current in a circuit consisting of a capacitor, inductor, and resistor will oscillate back and forth as the capacitor charges and discharges.

How It Works

The circuit layout is shown in the figure below. Initially the knife switch links the capacitor to the battery. Switching to complete the LRC circuit allows the capacitor to discharge. The current I in the circuit increases, as does the magneic field B inside the inductor. When the capacitor charge is zero, I and B are a maximum (the energy of the circuit is now stored in the inductor). As the...

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Thin Film Interference

What it shows:

Waves reflecting from two surfaces can interfere constructively and destructively. In this case it is light waves that are being reflected from the front and rear surfaces of thin soap or oil films. The interference produces a pattern of beautiful colors in white light, or dark and light bands in monochromatic light.

How it works:

Our two most visually dramatic illustrations of thin film interference use either a soap film suspended in air from a 19 cm diameter circular frame, or a very thin layer of oil floating on top of water....

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Sugar Syrups

What it shows:

Certain materials (sugar in this experiment) are optically active because the molecules themselves have a twist in them. When linearly polarized light passes through an optically active material, its direction of polarization is rotated. The angle of rotation depends on the thickness of the material and the wavelength of the light.

...

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Resonance Radiation/Absorption

What it shows:

For an electron to make a transition from one energy level to a higher one, it needs to absorb a photon who's energy is equal to the difference in the energy levels involved. When jumping back down, it will emit a photon of that same energy. These discrete energy separations are characteristic of the atom involved, and it's what provides an atom with its fingerprint line spectrum. Trying to induce a transition with a photon of different energy just doesn't work.

In this demonstration, light from a sodium source will be absorbed by sodium gas...

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