Electromagnetic Spectrum Lecture Notes

Introduction

• Electromagnetic Spectrum: The entire range of electromagnetic (EM) waves.
• Covers:
  • Origin of EM waves
  • Behavior when absorbed

Characteristics of Electromagnetic Waves

• Type: Transverse waves
  • Oscillate perpendicular to energy transfer direction (up and down)
• Speed in Vacuum: 3 × 10^8 meters per second
• Speed in Mediums: Varies; can lead to refraction (wave direction changes)

Types of Electromagnetic Waves

• Continuous Spectrum: EM waves are part of a continuous spectrum.
• Differentiation:
  • Wavelength and Frequency: Inversely related
    • As frequency increases, wavelength decreases
• Order of Waves (by decreasing wavelength/increasing frequency):
  • Radio Waves
    • Largest wavelength, smallest frequency
  • Microwaves
  • Infrared
  • Visible Light
    • Detectable by human eyes; gives colors
    • Colors: Red, Orange, Yellow, Green, Blue, Indigo, Violet (ROYGBIV)
  • Ultraviolet
  • X-rays
  • Gamma Rays
    • Smallest wavelength, largest frequency

Memorization Tips:

• Visible Light: Start in the middle and work outwards.
• Ionizing Waves: Ultraviolet, X-rays, Gamma rays (on the right, can cause cell damage).
• Communication Waves: Microwaves, Radio waves (on the far left).

Origins of Electromagnetic Waves

• Radioactive Decay: Emits gamma rays.
• Energy Level Changes: Electrons dropping levels emit visible, ultraviolet, and X-rays.
• Molecular Vibration: Generates infrared radiation.
• General: Radiation emitted by various sources everywhere.

Interaction of Electromagnetic Waves

• Travel: Can move through the universe, even across empty space.
• Contact Outcomes:
  • Reflection
  • Absorption
  • Transmission
  • Combination of above (e.g., some waves reflected, others absorbed)

Conclusion

• Summary of electromagnetic waves and their properties.
• Encouragement to review and understand the spectrum and its components.