Presentations

Sonometer

What it shows:

The effect of length, tension, diameter, and kind of material on the pitch of a vibrating string is demonstrated. One may also show the harmonics of a vibrating string.

How it works:

The sonometer is a long hollow wooden box along the top of which are stretched one or more strings rigidly attached to the box at one end, with provision at the other for changing their tension. If there is just one string, it's known as a monochord. The monochord illustration is from John Tyndall's book entitled Sound, (… Read more about Sonometer

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.

Spherical Blackboard

What it shows:

You can use a spherical blackboard for many things, including the teaching of geographical coordinates, as a model for a closed Universe, or simply as a mathematical shape.

In the non-Euclidean geometry of the sphere, a circle will have a circumference greater than 2πr and an area greater than πr2. A triangle’s angles will add to more than 180°, and two parallel lines, called Great Circles, will converge.

A Universe with a density parameter Ω greater than unity will have too much mass to overcome its own… Read more about Spherical Blackboard

Elastic Light

What it shows: 

The redshifted spectrum of galaxies and quasars is due to an expanding universe and can be expressed as the ratio of the scale factor of the present Universe to that of the Universe when the light was emitted. You can think of this as the light being s-t-r-e-t-c-h-e-d as the Universe expands so it arrives with a longer wavelength.

How it works: 

A 50cm × 10cm strip of dental dam with a wave drawn on it, attached at one end to a post and the other end free to pull. A wooden dowel at the pulling end ensures an even… Read more about Elastic Light

Bernoulli Beach Ball

What it shows

Bernoulli's principle shows the velocity dependence of pressure in a fluid. Here, fast flowing air creates a zone of low pressure that holds a beach ball aloft.

beach ball held aloft by fast flowing air from a blower

How it works

Here we have a beach ball held in the air stream from a… Read more about Bernoulli Beach Ball

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