Electromagnetic Spectrum and Waves Demonstrations

The electromagnetic spectrum covers all types of electromagnetic radiation, from radio waves to gamma rays. This category examines the range of wavelengths and their different properties. Understanding the electromagnetic spectrum helps explain communication technologies, medical imaging, and natural phenomena such as light and heat.

Demonstration	Materials	Difficulty	Safety	Summary
Doppler Ball	★★★	★☆☆	★☆☆	A Doppler ball contains a speaker that emits a constant tone. When the ball is thrown or swung on a string, the pitch of the sound changes due to the Doppler Effect, demonstrating how relative motion alters perceived frequency.
Slinky Waves	★☆☆	★☆☆	★☆☆	A stretched slinky can be used to model both longitudinal and transverse waves. By pushing or flicking one end of the slinky, students can see how wave energy travels through the coils.
Double Slit Experiment with Water Waves	★★★	★★☆	★☆☆	A tank of water with two slits in a barrier demonstrates how waves interfere. Circular water waves passing through the slits overlap to produce alternating regions of reinforcement and cancellation, creating an interference pattern that illustrates wave behavior.
Breaking Glass with Sound	★★★	★★★	★★★	A thin-walled wine glass can be shattered by sound if it is exposed to a tone at its natural resonant frequency. When the sound drives the glass strongly enough, vibrations build until the glass breaks.
Electromagnetic Shielding with a Faraday Cage	★★☆	★☆☆	★☆☆	An AM/FM radio is placed inside a Faraday cage to demonstrate how the cage blocks electromagnetic waves, preventing the radio from receiving signals.
Measuring the Speed of Light With a Microwave	★★☆	★★☆	★★☆	By heating a layer of marshmallows in a microwave without the rotating tray, you can observe melted spots that mark the peaks of a standing wave. Measuring the distance between these spots and combining it with the microwave’s frequency allows you to calculate the speed of light.
Microwave Hot Spots With Marshmallows	★★☆	★☆☆	★★☆	Marshmallows are heated in a microwave with and without the rotating tray to reveal the uneven distribution of energy inside the oven. This demonstrates how microwaves create hot and cold spots due to their wave pattern.
Black Light Fluorescence	★★★	★★☆	★★☆	Shine an ultraviolet (UV) “black light” on common items to reveal fluorescence. Students observe which materials glow and test mixtures (such as vitamins with vinegar) to explore how UV excitation produces visible light.
Doppler Effect with Water Waves	★★☆	★★☆	★☆☆	The Doppler Effect can be modeled using water waves. When a source of ripples moves through still water, the wavefronts bunch up in front of the moving source and spread out behind, showing how relative motion affects wave frequency.
Double Slit Experiment with Light	★★★	★★☆	★★☆	The double slit experiment with light shows how photons exhibit both wave and particle properties. A monochromatic light source passing through two slits produces an interference pattern on a screen, even when photons are sent one at a time.
Slinky Seismic Waves	★☆☆	★☆☆	★☆☆	This activity uses one or two slinkies to model how earthquakes generate P-waves, S-waves, and surface waves. The simple demonstration helps students visualize how energy travels through the Earth and why surface waves cause the most damage during earthquakes.
Harmonic Knives	★☆☆	★☆☆	★☆☆	This demonstration shows how a knife vibrates when struck and how holding it at different points changes the sound produced. By gripping the knife at a node, vibrations continue and produce a clear tone, while holding at an antinode dampens vibrations and creates a dull sound.
Radiometer	★★☆	★★☆	★☆☆	This demonstration shows how light energy can be transformed into both thermal and mechanical energy using a radiometer. The black sides of the vanes absorb more light and heat up more than the white sides. Air molecules striking the heated black surfaces gain more energy and rebound with greater force than those striking the white sides, causing the vanes to spin. A partial vacuum inside the bulb reduces resistance, making the effect easier to see.
Three Polarizing Filters	★★☆	★☆☆	★☆☆	This demonstration shows that two crossed polarizers block all light, but inserting a third polarizer at 45° between them transmits light - an effect explained by polarization, state preparation, and superposition. It offers an accessible, visual introduction to quantum ideas using classical optics.
Speed of Sound with a Resonance Tube	★★☆	★★☆	★☆☆	Use a water-filled resonance tube and tuning forks to find two resonance lengths for each frequency. From these lengths, determine the wavelength and calculate the speed of sound in air, with or without an end correction.
Atomic Spectra With a Diffraction Grating	★★☆	★★★	★★★	Using a diffraction grating and a gas discharge tube, you can observe the unique emission lines of different elements. These distinct line patterns reveal the quantized energy levels of electrons in atoms.
Microwaving Grapes to Create Plasma	★☆☆	★★☆	★★★	When two grapes slices are microwaved while touching, the microwave energy concentrates at their point of contact, creating an intense electric field strong enough to strip electrons from atoms. This ionizes the material and produces glowing plasma inside the microwave.

Materials
★☆☆ Easy to get from supermarket or hardware store
★★☆ Available in most school laboratories or specialist stores
★★★ Requires materials not commonly found in school laboratories

Difficulty
★☆☆ Can be easily done by most teenagers
★★☆ Available in most school laboratories or specialist stores
★★★ Requires a more experienced teacher

Safety
★☆☆ Minimal safety procedures required
★★☆ Some safety precautions required to perform safely
★★★ Only to be attempted with adequate safety procedures and trained staff