Lecture Notes: Electromagnetic Spectrum and Wave-Particle Duality

Electromagnetic Spectrum Overview

• Definition: The spectrum of all electromagnetic radiations, organized by their energy, frequency, and wavelength.
• Order and Characteristics:
  • Energy, frequency increase from left to right.
  • Wavelength decreases from left to right.
  • Gamma rays: Lowest wavelength, highest frequency, highest energy.

Regions of the Spectrum

• Beyond Visible Region:
  • Ultraviolet (UV), X-ray, Gamma ray: High energy, high frequency, low wavelength.
• Visible Spectrum:
  • Spectrum of colors, from red (low energy) to violet (high energy).
• Beyond Visible Region:
  • Infrared (IR): Detect heat, used in night vision technology.
  • Microwave: Lower energy than visible light; used in microwave ovens.
  • Radio Waves: Used in FM/AM radios, Wi-Fi, and cellular signals; longest wavelengths, lowest frequency, and energy.

Energy, Frequency, and Wavelength

• Photon Energy: Related to frequency; more photons increase total energy.
• Wave-Particle Duality:
  • Electromagnetic radiation exhibits both wave and particle characteristics.
  • Photon: Particle of light, an energy packet, no material mass.

Wave-Particle Duality Concept

• Dual Nature: Electromagnetic radiation acts as both waves and particles.
• Scientific Proof:
  • Radio waves demonstrate wave properties through frequency and amplitude.
  • Experiments validate energy packet nature of photons.

Broglie Hypothesis

• Wave-Particle Duality Extended: Applies to all particles, not just electromagnetic radiation.
• Broglie Relationship: Relates wave and particle nature of particles.
• Equation: [ \lambda = \frac{h}{mv} ]
  • ( \lambda ): Wavelength
  • ( h ): Planck's constant
  • ( m ): Mass of the particle
  • ( v ): Velocity of the particle

Practical Examples

• Fastball Example:
  • Wavelength too small to measure (10^-35 m), making wave property unobservable.
• Electron in Hydrogen Atom:
  • Observable wavelength (10^-10 m), comparable to the size of the atom, proving wave property.

Summary

• Wave-Particle Duality: Extends to all particles; observable in small particles like electrons.
• Scientific Attitude: Assume duality exists unless proven otherwise.
• Class Focus: Understand and perform calculations using Broglie relationship.

Next Topic

• Continuous and Line Spectrum: Will lead to understanding atomic structure.
• Note: Class ended early due to remaining time from previous sessions.