α, β, γ, n Sources and Detection

What it shows:

Radiations originating from atomic and nuclear processes are classified into four types:

charged particulate radiation consisting of
1. heavy charged particles (α)
2. fast electrons (β)
uncharged radiation consisting of
3. electromagnetic radiation (γ, x-ray)
4. neutrons (n)

The interaction processes of each type of radiation explain their penetrability through matter, their difficulty or ease of detection, and their danger to biological organisms. The interactions of these radiations with matter are unique and the...

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Greenhouse Bottles

Simulation of the greenhouse effect with silvered and unsilvered glass bottles.

What it shows:

Heat energy readily escapes from a clear glass flask, but is trapped inside a silvered flask which rapidly heats up.

How it works:

Two 2L flat bottom Florence flasks, one clear and one silvered (see reference), have identical 10Ω, 25W resistors placed inside them connected in series to a DC supply 1 These resistors act as good sources of infrared radiation. The clear flask readily transmits the IR, but the silvered...

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Viscous Flow of Bread Dough

Bread dough is stiff but still flows. A big blob of foodstuff that slumps over time, like Silly Putty but large and edible.

Make bread dough enough for a couple loaves, and knead it stiff enough that a round ball of dough takes half an hour to slump to half its original height. Place on a plate, put a camera on it. Project the image at the beginning, just as the dough ball is released, and again some time later, after viscous flow.

Pendulum Waves

What it shows:

Fifteen uncoupled simple pendulums of monotonically increasing lengths dance together to produce visual traveling waves, standing waves, beating, and random motion. One might call this kinetic art and the choreography of the dance of the pendulums is stunning! Aliasing and quantum revival can also be shown.

How it works:

The period of one complete cycle of the dance is 60 seconds. The length of the longest pendulum has been adjusted so that it executes 51 oscillations in this 60 second period. The length of each...

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Diamagnetic Levitation

What it shows:

Stable levitation of one magnet by another is usually prohibited by Earnshaw's Theorem, but the introduction of diamagnetic material at special locations can stabilize such levitation. The demonstration is a replica of an experiment described by M.D. Simon and A.K. Geim1 and is pictured in the photograph. The illustration is from their paper.


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Uranium Block

What it shows:

This block of uranium is of great historical significance -- it is a remnant of the WWII German Atomic Bomb Project. It was brought to Harvard by Prof. Edwin C. Kemble, Physics Dept. Chairman and also Deputy Science Director of the ALSOS mission in 1945. The American ALSOS mission was an intelligence effort to discover the extent of German progress toward atomic weapon development and its ultimate purpose was to secure all the uranium ore the Germans had confiscated during the war and finally close the books on the German program to build an atom...

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Precipitation of Silver Chloride

Sodium chloride solution is added to silver nitrate solution and a white precipitate of silver chloride is instantly formed.

The silver nitrate solution is around 0.1M, and the sodium chloride solution around 0.5M. Pour the sodium chloride sol'n into the silver nitrate to avoid leaving traces of silver nitrate in the empty beaker.

Wear safety glasses and gloves to prepare and perform this demonstration.

Bean Buoyancy

What it shows

Objects with a density lower than the fluid that they are submerged in will float; objects with a greater density will sink. This is shown using a brass ball and ping-pong ball of equal size, and a sea of beans.

How it works

500g of navy beans form a rather coarse fluid in a 1.5L glass beaker. Embedded in the beans is a ping pong ball, and sitting on the surface is a brass ball, 4cm in diameter. This fluid needs to have flow 'induced', and this is done by shaking the beaker side to side. The ratio of densities of brass:beans:ping-pong is approximately...

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Paramagnetism of Oxygen

What It Shows

A large magnet with a small cylindrical gap allows a stream of liquid nitrogen to pass over and through. Poured liquid oxygen hangs between the poles in the strong field until it boils away.

How It Works

Pour the liquid nitrogen first, slowly over the pole pieces. The result is nothing but vapor condensation and crackling plexiglas; the liquid does not interact with the large magnetic field.

Next pour the liquid oxygen slowly over the pole pieces, and it collects in the gap between the poles. It might take two or three short pours to get the...

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