Run towards the blackboard carrying a tuning fork...
What it shows:
Waves emitted from a moving source are Doppler shifted to higher frequencies when moving towards the observer, and shifted to lower frequencies when moving away from the observer. In this situation the source is moving away from you, but the raised frequency sound is reflected back interfering and causing beating. Read more about Doppler Tuning Forks
The following is a sequence of experiments that can accompany a standard lecture on electromagnetic waves. The entire sequence is quite long and you may not want to do it all in one lecture.
1) The voltage variation along the length of a dipole transmitting antenna can be made evident. The intensity variation of a fluorescent light bulb, held near the antenna, shows the voltage to be maximum at the ends and minimum in the middle of the dipole. Read more about Radio Wave Properties
Light is transmitted by a bundle of optical fibers and/or a coiled length of plastic rod, regardless of the twists and turns in the path it must negotiate. Total internal reflection keeps the light confined. Read more about Fiber Optics
In quantum mechanics, it is possible for a particle to tunnel through a potential barrier because its wave function has a small but finite value in the classically forbidden region. Here we use FTIR as an optical analog of this quantum mechanical phenomenon. Read more about Tunneling Analog
1m diameter rubber sheet acts as curved space for ball bearing masses.
What it shows:
In general relativity, gravity is replaced by a curved space geometry, where the curvature is determined by the presence and distribution of matter. Objects move in straight lines, or along geodesics, but because of the curvature of space, their paths will simulate the effect of gravitational attraction. This demo gives a two dimensional view of warped space. Read more about Gravitational Field Surface
The strength of a material in tension or compression will be affected by discontinuities in its surface structure. This can be demonstrated for glass using microscope slides, and the comparison of failure stress before and after the removal of surface scratches. Read more about The Surface Treatment of Glass
Vinegar and two different amounts of baking soda in plastic soda bottles with balloons.
Two 500ml PETN soda bottles of the same make, split a bottle of vinegar between them.
11" balloons are pre-inflated with dry air, with care taken not to stretch the neck of the balloon. Into the balloons with a funnel go one, two teaspoons of baking soday. With 250 ml of vinegar, that's like six liters of gas potential if one carbon dioxide comes from one acid hydrogen ion. Read more about Limiting Reagent, Vinegar or Baking Soda?