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TV Color Perception

What it shows:

The full spectrum of colors (including white) in a television picture is produced by the additive mixing of only three colors: red, green, and blue.

How it works:

In a color television tube, three separate electron beams are focused so as to strike the appropriate phosphor dot on the screen. By looking at the television screen under considerable magnification, one can clearly see that there are only three phosphors which are stimulated by the electron beam(s). The apparatus is diagrammed below.

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Reaction of Hydrogen and Oxygen

Blue balloon with hydrogen, green balloon with helium, red balloon in back with hydrogen and oxygen mixture, and, on a cart, a red water balloon on large watch glass. Candle on a stick with matches, and a needle in the end to prick the water balloon.

Safety glasses and hearing protection is required for the demonstrator and anyone else who can't cover their ears for the red balloon.

Shoot the Monkey

Monkey released from platform is shot by simultaneously fired cannon.

What it shows:

This is a demonstration of the independence of the horizontal and vertical components of velocity of a projectile. Often referred to as "the monkey and hunter," the problem is the following. A hunter (at ground level) aims a gun at a monkey hanging from a branch high in a tree. The monkey, being very intelligent, does not want to be shot. It knows that light travels faster than bullets and reasons that, if it lets go of the branch the instant it sees the flash of the gun,...

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Ring of Fire

ring of fire

What it shows:

In explaining the electron orbits in the Bohr atom, de Broglie's principle of particle wave duality allows you to treat the electrons as waves of wavelength nλ = 2πr where r is the radius of the orbit. Then the only...

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Schlieren Optics

Optical technique that allows us to see small changes in the refractivity of air and other transparent media.

What it Shows

Refraction due to inhomogeneity in air is made visible by our single-mirror schlieren optics setup. The...

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Reaction of Sodium and Water

Sodium undergoes a reaction with water.

A liter of warm water in large pyrex vessel, covered with fine mesh stainless steel screen, is on a stool close by in-floor vent hood.  Add a few drops from the phenolphthalein indicator bottle.

Using the long forceps, pick out a pea size lump of sodium metal from the mineral oil in the small beaker. Wipe off the lump on the dry paper towels. With the vent fan running, lift the edge of the screen and drop in the sodium metal. Replace the screen and get back.

The sodium will from a hissing ball of molten metal, which bounces...

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Newton's Apple

Apple electronically released from platform; fall time given by special circuit and digital display.

What it shows:

This is a free-fall-from-rest experiment in which an apple (or any other object of comparable size) is dropped from the lecture hall ceiling into a catching bucket on the floor. By measuring the (1) distance and (2) duration of the fall, an accurate (± 0.022%) determination of the acceleration due to gravity can be made:

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Cavendish Experiment

Calculation of gravitational constant, with accompanying apparatus model.

What it shows

The gravitational attraction between lead spheres. The data from the demonstration can also be used to calculate the universal gravitational constant G.

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