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 refraction can be caused by changes in the density, temperature, or pressure of the air immediately...

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Nuclear Fission

What it shows:

In a nuclear reactor or atom bomb, a fissile material such as 235U can capture a neutron. The resulting unstable nucleus fragments into two smaller nuclei, releasing energy and several neutrons (a typical equation is given below). Each of these neutrons can in turn cause the fission of a 235U nucleus. If there is above a critical concentration of fissile material, this chain reaction will continue unaided, and if unregulated can result in a very loud bang.

n + 235U → 236U* → 141Ba + 92Kr + 3n

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Telescope Resolution

What it shows

A telescope (with video output) at the front of the lecture hall is focused on two point light sources at the rear of the hall. Although the light sources are only 1/2 mm apart, they are readily resolved. The Rayleigh limit of resolution can be clearly shown by reducing the telescope aperture to the point where the two light sources can barely be resolved, similar to the following images (from: Cagnet/Francon/Thrierr, Atlas of Optical Phenomena). At the Rayleigh limit the centers of both point sources coincide with the the first minimum of the other source....

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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 orbits allowed are those which are integer...

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Bouncing Light Beam

What it shows:

As a simulation of atmospheric refraction, this demonstration shows the gradual and continuous bending of light due to a gradient in the optical density of the medium. In this case the variable refracting medium is a tank of sugar water with a vertical gradient in the concentration of sugar and a HeNe laser provides the light beam. It can be used as a model of mirage formation (except that the direction of increasing refractive index is in the opposite direction) or even as a representation of the refraction of seismic waves through the Earth's...

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Relativity Train

What it shows:

The Relativity Train is a realization of the famous Einstein gedanken experiments involving traveling trains carrying clocks and meter sticks. The demonstration is used to show how the preservation of the postulated constancy of physical laws and the speed of light in all inertial frames requires length contraction and time dilation in the train frame relative to the lab frame of reference. The demonstration is, of course, not a real experiment but rather a visual means of showing (without using any equations) how length contraction and time dilation are...

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Erector Spinae Muscle Forces

A realistic model of the forces in the erector spinae muscles that support the back when bent over.

What it Shows:

This is an analysis of the tensions in muscles and forces on joints as an application of torques in static equilibrium situations. The muscles involved in supporting the human torso in a stooped position are realistically modeled, and the extraordinary large forces calculated and demonstrated.

How it Works:

When bending over into a stooped position, the principal muscles which support the back are the erector...

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Newton's Rings

What it shows:

Waves reflecting from two surfaces can interfere constructively and destructively. In this case it is light waves that are being reflected at glass/air and air/glass interfaces. The interference produces a concentric ring pattern of rainbow colors in white light, or dark and light rings in monochromatic light.


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