Electromagnetic Spectrum Lecture Notes

Introduction

• The electromagnetic spectrum encompasses all electromagnetic (EM) waves.
• EM waves are transverse waves.
  • Oscillate perpendicular to the direction of energy transfer.
• In a vacuum, they travel at 3 x 10^8 meters/second.
• Speed varies in different mediums, leading to refraction (change in direction).

Types of Electromagnetic Waves

• Seven Basic Types:
  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays
• Part of a continuous spectrum differentiated by wavelength and frequency.
  • Inversely related: as one increases, the other decreases.

Characteristics of Waves

• Radio Waves:
  • Largest wavelength, smallest frequency.
  • Wavelengths can be multiple kilometers.
• Gamma Rays:
  • Smallest wavelength, highest frequency.
  • Wavelengths less than a thousandth of a nanometer.

Visible Light

• Human eyes detect only visible light.
• Wavelengths within this region provide different colors.
• Colors of the rainbow can be remembered as ROYGBIV:
  • Red, Orange, Yellow, Green, Blue, Indigo, Violet.

Order and Classification

• Memorizing order: start with visible light and move outward.
• After Violet: Ultraviolet.
• Before Red: Infrared.
• Right of Visible Light:
  • Ultraviolet, X-rays, Gamma rays (ionizing, can damage cells).
• Left of Visible Light:
  • Microwaves, Radio waves (used in communication).

Origin of Electromagnetic Waves

• EM waves originate from various sources.
• Radioactive decay: emits gamma rays.
• Electron energy level drops: emit visible light, ultraviolet, X-rays.
• Molecular vibration: generates infrared radiation.

Interaction with Matter

• EM waves can be reflected, absorbed, or transmitted.
  • Often a combination of these interactions occurs.
• Example: some waves might be reflected while others are absorbed.

Conclusion

• Understanding the electromagnetic spectrum involves knowing the types, characteristics, and interactions of EM waves.
• Memorizing the order of waves and their applications is important for understanding their effects and uses.