Para and Diamagnetism

What it shows: 

The behavior of a substance in a non-uniform magnetic field will depend upon whether it is ferromagnetic, paramagnetic or diamagnetic. Here we test different substances to see how they are influenced by a magnetic field.

How it works: 

We have a collection of samples (listed in table 1) that exhibit well the three magnetic properties. Diamagnetic substances have a negative relative permeability (susceptibility); paramagnetic substances have positive.

Ferromagnetic substances have...

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Hotplate Mirage

What it shows:

A beam of light is distorted due to turbulent convection currents in air. This is a model of atmospheric distortion that affects seeing conditions in ground based optical and infrared astronomy.

How it works:

Turbulent air is provided by an electric stove ring, that heats the air above it as the warm earth dues to air sitting above it. The turbulent currents set up alter the refractive index of the air in a disordered and rapidly changing way. Light from a point source passing through these conditions is blurred...

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Uncertainty Principle

What it shows:

A pulse-modulated electromagnetic signal is simultaneously displayed in the time domain (on an oscilloscope) and in the frequency domain (on a spectrum analyzer). Using ∆n for the frequency spread (uncertainty in frequency) and ∆t for the duration of the pulse (uncertainty in the time domain), the frequency-time uncertainty relation is given by 1

∆n ∆t ≥ 1/

By progressively shortening the length of time that the carrier signal is on, the inverse relation between pulse length and spectral-energy...

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Reactions of Li, Na, and K with Water

Lithium, sodium, and potassium undergo reactions with water.

Two liters 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, and a few drops of 1M hydrochloric acid if the warm tap water turns pinkish.

Video camera is clamped to the stool leg, and pointed at the bottom of the beaker. Before class, frame the shot and focus on the center of the beaker.

Using the long forceps, pick out the coil of lithium wire from the mineral oil in...

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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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Hertz Resonator

What it shows:

The transmission and detection of radio frequency electromagnetic radiation by use of LC oscillator circuits recreates the discovery by Hertz of a method to generate and detect electromagnetic waves.

How it works:

The core of the apparatus (figure 1) is a series LRC circuit (the R provided by the circuit resistance). The inductor L is a 1m diameter loop made of 1 inch copper tubing which also serves as the radiating antenna. A transformer 1 supplies 15kV to charge up the capacitor 2 until...

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Hot Road Mirage

What it shows:

There are various types of mirages possible, the details depending on whether the hot air is above or below the cool air and how sharp the transition is from cool to warm. This demonstration simulates what happens when a dark asphalt road gets much hotter than the air around it--the air next to it becomes hotter than the higher air and light traveling through this temperature gradient is bent so much that it appears reflected. The shimmering water on a road's surface or the blue oasis in the desert are natural examples of blue skylight being...

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Fraunhofer Absorption

What it shows:

Sodium 'D' line absorption showing up as a black line in the yellow of a continuous spectrum. Good as a simulation of the sodium portion of the Fraunhoffer absorption spectrum caused by atoms in the solar atmosphere; it does not however, resolve the 5890/5896Å doublet.

How it works:

As in the Sun, which is a black body source surrounded by an atmosphere of cooler gas containing many heavy atoms including sodium, we can set up a black body spectrum using a slide projector, and provide a hot sodium 'atmosphere' using...

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