PhysicsChapter 11: Electromagnetic Waves
The Electromagnetic Spectrum
Introduction
The electromagnetic spectrum is the complete range of electromagnetic waves arranged according to wavelength or frequency. All electromagnetic waves consist of changing electric and magnetic fields and can travel through a vacuum. In vacuum, all electromagnetic waves travel at approximately: c = 3.0 × 10⁸ m/s
Definition
Order of the Spectrum
From longest wavelength and lowest frequency to shortest wavelength and highest frequency: Radio → Microwave → Infrared → Visible → Ultraviolet → X-rays → Gamma rays
Frequency and Wavelength
Wave speed is given by: **c = fλ where: `c` = speed of electromagnetic waves in vacuum `f` = frequency `λ` = wavelength Since `c` is constant in vacuum: higher frequency → shorter wavelength lower frequency → longer wavelength**
Energy
For electromagnetic radiation: **E = hf where: `E` = photon energy `h` = Planck's constant `f` = frequency Therefore: higher frequency → greater photon energy**
Shared Properties
All electromagnetic waves: can travel through vacuum; carry energy; travel at the same speed in vacuum; can show reflection, refraction, diffraction and interference.
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.The Electromagnetic Spectrum
Sticky Notes · Quick Revision
EM SPECTRUM
- Radio → Microwave → IR → Visible → UV → X-ray → Gamma
VACUUM SPEED
- 3 × 10⁸ m/s
60-second revision
- Radio → longest λ.
- Gamma → shortest λ.
- **c=fλ**
- Higher `f` → lower `λ`.
- Higher `f` → higher photon energy.
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