Presentations

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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Faraday Induction

What it shows:

The mathematical description of electromagnetic induction as formulated by Maxwell and Faraday requires two different sets of equations to calculate the induced voltage, depending on whether the coil is stationary and the magnet moving or vice versa. In fact, as this demonstration shows, the voltage is the same as predicted by the two sets of equations.

How it works:

The apparatus is identical to demonstration Faraday's Law, and is described in detail there. Briefly, it consists of a galvanometer hooked up to a...

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Liquid Crystal Sheets

What it shows:

The selective reflection of a specific wavelength of light through a chiral nematic liquid crystal is temperature dependent and forms the basis for LCD thermograms and thermometers.

How it works:

Liquid crystals are an intermediate state of matter or mesophase between (crystalline) solid and liquid. Substances that have a mesophase have a non-flexible rod-like molecular structure. Although in a liquid phase, the shape of the molecule and intermolecular forces means that the molecules retain a common preferred...

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Binary Star

Two small closely mounted bulbs simulate resolution problems.

What it shows:

The ability to resolve two closely separated stars depends upon the aperture size of the observing instrument. Here two tiny bulbs represent stars that are barely resolvable by human eyes across the lecture hall.

How it works:

The light collected from two stars by the eye (or by a telescope mirror) are themselves geometric point sources but are circular diffraction fringes

The light from a distant star is not detected as a geometric point...

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Mixing Ethanol and Water

Ethanol and water are mixed in volumetric glassware, showing a volume decrease and a temperature increase.

Two 250 ml graduated cylinders are filled to the line with water and ethanol (100%). A temperature probe shows both at room temperature. The temperature probe is then moved to an empty 500 ml graduated cylinder, and the contents of the two smaller cylinders poured simultaneously to mix well. 

The temperature of the mixture rises about 8°C, and the volume decreases to 480 ml just after mixing, clearly visible on the scale of the 500 ml cylinder, and to the class by...

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Incompressibility of Water

What it shows

The bulk modulus of water is about 2.2 x 109 Pa, which means that a change of 1 N/m2 of external pressure on the liquid is able to change a given volume of it by a factor of 4.5 x 10-10 (for comparison, the same pressure change would produce a volume change of about 7 x 10-6 for air and 7 x 10-12 for cast steel ). So if we can completely fill a Florence flask with water, we can use it as a hammer to drive a nail into a board!

...

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Length Measurement

[M | t | ★] 
Standard meter sticks and selection of cubic volumes. 

What It Shows

No temperature-controlled platinum rods here – just some sticks that are very close to a meter in length. Standard meter sticks as well as cubic centimeters and decimeters are available for reference and/or comparison. Other volumes include a 22.4 liter cube (to get the sense of the size of a mole of gas). Sets of calibrated weights include both metric and English standards from milligrams to several kilograms. Various types of analytical balances and scales are also available:...

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