Waves, Sound & Light
Waves transfer energy without transferring matter. Sound and light are both waves, but they travel very differently.
Wave Properties
Wavelength (λ): distance between peaks.
Frequency (f): waves per second (Hz).
Amplitude: height of wave (related to energy).
Wave speed: v = fλ
Transverse vs Longitudinal
Transverse: vibration perpendicular to wave direction (light, water waves).
Longitudinal: vibration parallel to wave direction (sound — compressions and rarefactions).
Sound
Sound needs a medium (can't travel in vacuum). Speed in air ≈ 343 m/s. Higher frequency = higher pitch. Higher amplitude = louder. Humans hear 20 Hz–20,000 Hz.
The Electromagnetic Spectrum
EM waves need no medium. All travel at speed of light (3×10⁸ m/s). From lowest to highest frequency:
Radio → Microwave → Infrared → Visible light → UV → X-rays → Gamma rays
Reflection & Refraction
Reflection: wave bounces off surface (angle in = angle out).
Refraction: wave bends when entering new medium (why straws look bent in water).
FAQ
Why is there no sound in space? Sound needs a medium to travel. Space is nearly a vacuum.
What color has the highest energy in visible light? Violet — highest frequency.
Quick Quiz
Test what you just learned. Choose the best answer for each question.