Science Lecture on Electromagnetic Waves

Introduction to Electromagnetic Waves

Electromagnetic waves are pervasive and involved in many daily activities (e.g., radio, microwaves, sunlight).
Key learning objectives:
- Compare relative wavelengths and frequencies of electromagnetic waves.
- Understand relationships between wavelength, frequency, and energy.

Wave: A disturbance in space.
Crest: The highest point in a wave.
Trough: The lowest point in a wave.
Amplitude: Distance from midpoint to crest/trough; larger amplitude means more energy.
Wavelength: Distance between successive identical parts (crest to crest or trough to trough).
Frequency: Number of waves produced in one second.

Proposed by Orsted and Faraday:
- Created by vibrations between electric and magnetic fields.
- Can travel through a medium or vacuum.
Speed of EM waves in vacuum: 300 million meters per second (3 x 10^8 m/s).
Relationship:
- As wavelength decreases, frequency increases.
- Light from the sun takes about 8 minutes to reach Earth.

Radio Waves: Longest wavelength (>10^-1 meters), shortest frequency (<3 x 10^9 Hz).
Gamma Rays: Shortest wavelength (~10^-11 meters), highest frequency (>3 x 10^19 Hz).
Visible Light: Only EM waves visible to humans, essential for photosynthesis.
Ultraviolet Rays: Cause sunburns; not visible to the human eye but seen by some insects.
Microwaves: Used in cooking and communications.
X-Rays: High energy; used in medical imaging.
Infrared Radiation: Detected as heat, used in night vision and security.

Students are instructed to create a chart comparing sizes of EM waves using various objects to represent their wavelengths.

Recap of the electromagnetic spectrum:
- Longest wavelength and lowest energy: Radio waves.
- Shortest wavelength and highest energy: Gamma rays.
Importance of understanding EM waves in everyday life and various technologies.
Encouragement to engage and learn more about science.