Electromagnetic Spectrum Notes

Electromagnetic Spectrum

Introduction

  • The electromagnetic spectrum is the entire range of electromagnetic waves.
  • We will cover the origin and absorption of these waves.

Nature of Electromagnetic Waves

  • EM waves are transverse waves, meaning they oscillate perpendicular to the direction of energy transfer.
  • In a vacuum, all EM waves travel at the same speed: 3×1083 \times 10^8 meters per second.
  • In different mediums, EM waves travel at different speeds, leading to refraction (change in direction).

Electromagnetic Spectrum Types

  • The electromagnetic spectrum is divided into seven basic types.
  • These types are part of a continuous spectrum differentiated by wavelength and frequency.
Wavelength and Frequency Relationship
  • Wavelength and frequency are inversely related: when one increases, the other decreases.
  • Reading the spectrum from left to right:
    • Frequency increases.
    • Wavelength decreases.
  • Radio waves:
    • Largest wavelength.
    • Smallest frequency.
  • Gamma rays:
    • Smallest wavelength.
    • Largest frequency.
  • Wavelength range: from kilometers (radio waves) to less than a thousandth of a nanometer (gamma rays).

Visible Light

  • Human eyes can only detect a tiny part of the spectrum called visible light.
  • Different wavelengths within the visible light region correspond to different colors.

Memorizing the Spectrum Order

  • Start with visible light in the middle and work outwards.
  • Colors of the rainbow: ROYGBIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet).
  • After violet: Ultraviolet.
  • Before red: Infrared.
Grouping for Memorization
  • X-rays and gamma rays are on the right side of the spectrum.
  • Ultraviolet, X-rays, and gamma rays are ionizing and can cause cell damage.
  • Microwaves and radio waves are used in communication and are on the far left.

Origin of Electromagnetic Waves

  • EM waves originate from various sources.
  • Radioactive decay can cause the emission of gamma rays.
  • Visible light, ultraviolet, and X-rays can be emitted when electrons drop down energy levels.
  • Vibrations of molecular bonds generate infrared radiation.
  • Radiation is emitted from various sources.

Behavior of Electromagnetic Waves

  • EM waves can travel across the universe through empty space.
  • When they interact with matter, they can be:
    • Reflected.
    • Absorbed.
    • Transmitted.
  • Sometimes a combination of reflection, absorption, and transmission occurs.