Overview
This lecture introduces the nature of electromagnetic (EM) waves, their production, properties, and the differences between mechanical and electromagnetic waves.
The Nature of Waves
- A wave is a disturbance that transfers energy from one place to another without moving matter.
- Mechanical waves require a material medium to transfer energy (e.g., sound waves, ocean waves).
- Electromagnetic waves do not require a medium and can transfer energy through a vacuum.
Production and Propagation of Electromagnetic Waves
- Electromagnetic waves are produced by oscillating (moving back and forth) or accelerated charged particles, such as electrons.
- These waves consist of electric and magnetic fields that vibrate perpendicular (90 degrees) to each other.
- EM waves propagate outward from the source into space as electromagnetic radiation.
Properties of Electromagnetic Waves
- EM waves can travel through vacuum (empty space) and do not need any material medium.
- EM waves always move at the same speed in vacuum: 3.0 × 10⁸ meters per second (the speed of light).
- The speed of light is constant in vacuum and is the universal speed limit; it can be slower in materials like glass or water.
Key Terms & Definitions
- Wave — A disturbance that transfers energy without transferring matter.
- Mechanical Wave — A wave that requires a medium (material) to transfer energy.
- Electromagnetic Wave (EM wave) — A wave that can transfer energy through a vacuum, consisting of oscillating electric and magnetic fields.
- Vacuum — An empty or free space without matter.
- Oscillating Charge — A charged particle moving back and forth, producing EM waves.
Action Items / Next Steps
- Reflect in your notebook: How are EM waves important in everyday life?
- Complete the five-item poster activity by filling in the correct concepts.
- Review pretest statements and indicate agree or disagree.
- Prepare for Lesson 2 on the proponents of electromagnetic theory.