Lesson 10: Waves & the Electromagnetic Spectrum
Waves transfer energy without transferring matter. From the sound in your ears to the light in your eyes to the X-rays in a hospital — all are waves, and they all obey the same fundamental relationship: wave speed = frequency × wavelength.
Key Concepts
Wave Properties
Amplitude: height of wave (related to energy/loudness/brightness). Wavelength (λ): distance between consecutive crests. Frequency (f): cycles per second, measured in Hz. Period (T = 1/f): time for one cycle.
Wave Equation
v = f · λ. Speed depends on the medium. For light in a vacuum: c = 3 × 10⁸ m/s. For sound in air: ~343 m/s. Frequency and wavelength are inversely proportional at constant speed.
Transverse vs. Longitudinal
Transverse waves: particles oscillate perpendicular to the direction of travel (light, water surface waves). Longitudinal waves: particles oscillate parallel (sound, seismic P-waves).
Electromagnetic Spectrum
All EM waves travel at c in vacuum. From longest to shortest wavelength (lowest to highest energy): Radio → Microwave → Infrared → Visible Light → Ultraviolet → X-ray → Gamma ray.
Wave Phenomena
Reflection (bounces off surface). Refraction (bends when speed changes at boundary). Diffraction (spreads around obstacles). Interference (waves add: constructive = louder/brighter; destructive = quieter/darker).
🔬 Virtual Lab: Wave Property Explorer
Adjust frequency and amplitude sliders. Watch the wave animate and see how the properties change.
✅ Check Your Understanding
1. If wave speed is constant and frequency increases, what happens to wavelength?
2. Which has the shortest wavelength on the EM spectrum?
3. In a transverse wave, particles oscillate: