The Electromagnetic Spectrum
📋 What it is
Light is one band of a huge spectrum of electromagnetic waves — radio to gamma — that need no medium.
🗣️ Coach says
Unlike sound, electromagnetic waves need NO material to travel — that’s why light and radio cross empty space. Visible light is just one narrow band of a giant family: radio, microwave, infrared, visible, ultraviolet, X-ray and gamma, differing only in wavelength and energy.
🧠 Memory hook
EM waves travel through empty space. Visible light = one thin band of the whole spectrum.
😂 Giggle
Why did the longitudinal wave feel squeezed?
Because it was always being compressed!
😲 Whoa!
Sunlight takes about 8 minutes to reach Earth across empty space — sound could never make that trip, because there’s no air out there to carry it.
✅ Quick check: What’s one big difference between sound waves and light (EM) waves?
Say your answer out loud first — then reveal.
Sound needs a material to travel through; light/EM waves can travel through empty space.
EM waves need no medium; sound does.
🧪 Try it! (2 minutes)
Point a TV remote (infrared) at a phone camera and press — you may "see" the invisible EM flash.