Electromagnetic Radiation Topic

Transmission Lines and Antennas

Concept 4 demos

FLIR thermal image of marshmallows showing bright yellow-orange hot spots at regular intervals against purple cooler regions, temperature scale from 21.5 to 41.3 degrees C

Standing Microwaves

Marshmallows in a microwave oven (turntable removed) heat unevenly, revealing the standing wave pattern through hot spots visible on a FLIR thermal camera. Measuring the spacing between hot spots gives …

Microwave oven on lecture bench with door open showing two styrofoam cups inside; infrared camera thermal image projected on wall behind shows temperature reading of 22.5 degrees

Microwave Heating

Microwaves selectively heat polar molecules (water) while leaving non-polar materials (styrofoam, air) unaffected. Students see this directly using an infrared camera to compare a water-filled cup with an empty cup …

Transmitter apparatus: black transformer on wooden base (left), two vacuum tubes in glass envelopes mounted on black base with copper loop and tuning coil, copper rod transmitting antennas extending horizontally, and receiver dipole with insulated center tube lying in front

High Frequency Radio Transmitter

A vacuum tube oscillator generates radio-frequency EM waves detected by a dipole receiver with a light bulb indicator. Demonstrates polarization (rotating receiver), standing waves (walking through the room), and inverse-square …

Tesla Coil

Concept 1 demo

Tesla coil on a plywood base in a lecture hall: red-wire secondary coil with aluminum toroid on top, copper spiral primary coil visible at the base, and a warning label about the 15-second operating limit

Tesla Coil

A spark-gap Tesla coil produces dramatic 75-cm arcs and wirelessly lights a fluorescent tube, demonstrating resonant energy transfer, high-frequency electromagnetic fields, and dielectric breakdown of air.

Electromagnetic Spectrum

Concept 3 demos

$Overhead projector with diffraction grating on lens, projecting a bright white central slit image flanked by symmetric rainbow spectra (red on outside, blue/violet on inside) onto the wall$

White Light Spectrum

Demonstrates that white light is composed of all visible wavelengths by dispersing it into a continuous spectrum with a diffraction grating. Provides a foundation for spectroscopy and the electromagnetic spectrum.

Phosphorescent Discraft Ultra-Star disc glowing green under UV light, partially shadowed by glass plate blocking part of the UV

Short & Long Wave UV

Glass transmits longwave UV but blocks shortwave UV, demonstrated using a phosphorescent disc as a visible indicator. A plastic container with CFL phosphor fragments shows a similar blocking effect. Students …

FLIR camera display showing false-color thermal image of an ice cube tray (cold, dark) and activated heat pack (hot, bright), with spot temperature 23.9°C and scale from -7.0 to 46.5°C

Infrared Camera

An infrared camera reveals thermal radiation from everyday objects, showing that all objects emit electromagnetic radiation and that materials have strikingly different optical properties in the infrared vs. visible spectrum. …