Electromagnetic Waves

Introduction

• Focus on electromagnetic waves
• Particle with electric charge generates an electric field
• Static field when charge is motionless

Acceleration of Charges

• Accelerating a charge generates a magnetic field
• Electric and magnetic fields are interconnected components of the electromagnetic field
• Disturbances in one field affect the other
• Movement propagates through space at the speed of light

Properties of Electromagnetic Waves

• Energy of wave depends on particle acceleration
• Categories of electromagnetic waves based on frequency:
  • Visible light
  • Infrared
  • Ultraviolet
  • Microwaves
  • X-rays
  • Radio waves
  • Gamma rays

Detection and Applications

• Most electromagnetic radiation is invisible
• Technologies allow detection and emission of waves
  • Microwave ovens
  • Telecommunications
  • Astronomy with space telescopes
• Astronomers use different types of waves for a detailed cosmic view

Emission of Radiation

• All objects emit electromagnetic radiation when charged particles move
• Temperature correlates with atomic agitation
  • Atoms consist of a positively charged nucleus and negatively charged electron cloud
  • Vibrating atoms emit electromagnetic waves
  • Higher temperatures = more energetic waves
• Example: Human body emits infrared radiation

Polarization of Waves

• Electron clouds vibrate chaotically (non-polarized waves)
• Controlled vibrations result in polarized waves
  • Types: Rectilinear, elliptical, circular polarization
• Radio antennas create rectilinearly polarized waves

Interaction with Matter

• Light interacts with objects based on polarization
  • Polarizers absorb certain polarizations
  • Example: 3D cinema technology

Wave Principles

• Waves can superimpose
  • Interference: Two crests combine or cancel out
  • Diffraction: Waves encounter obstacles or narrow slits
• Scattering: Light diffused in different directions due to atomic vibrations
  • Example: Blue sky due to scattering of higher energy blue light

Reflection and Refraction

• Reflection: Light bouncing back from surfaces
  • Conductive materials (like mirrors) cause currents that recreate the incident wave
• Refraction: Light changes direction and speed when entering materials
  • Atoms vibrate, emitting new waves that interfere with initial wave
  • Overall speed of light in materials is slower (but each wave moves at light speed)
  • Cherenkov effect: Light flashes when particles exceed light speed in a medium

Conclusion

• Electromagnetic waves play a crucial role in various physical phenomena and technologies.