Main Points of Presentation
- Define electromagnetic wave
- Who discovered the electromagnetic wave
- Properties of the wave
- Interaction with matter
- Relationship with particles
- Types of EM Waves
- Real uses of EM Waves
What is an Electromagnetic Wave?
Who Discovered Electromagnetic Waves?
Heinrich Hertz - 1800s German Physicist that proved the theory of electromagnetic radiation by Maxwell.
James Clerk Maxwell
Came up with the original theory of electromagnetic waves by noting that waves could be produced by changing electric and magnetic fields.
Used Maxwell's theory to prove existence of electromagnetic waves, starting with the radio wave.
He proved the existence of radio waves using two rods, in which, essentially, waves were picked up and he could see a spark there. His later experiments proved that this had all the properties of an electromagnetic wave.
James Clerk Maxwell
How are Electromagnetic Waves Made?
- Electric charge vibrates, and the surrounding electric field changes
- Magnetic field surrounding electric charge changes
- Vibrating electric charge is surrounded
- Surrounded by a changing electric/magnetic field
- Becomes a wave as the changing electric/magnetic fields continually create each other
In Layman's Terms...
- Electric Charge - Positive or negative
- Electric Field - Area around said electric charge
- Magnetic Field - Area around either a magnet or moving electric charge
Essentially, the positive or negative charge, or "thing," vibrates. The area around that charge begins to vibrate as well. Because the charge is in motion, it has a magnetic field, which changes while this is happening. The changing magnetic field creates a changing electric field, which creates a changing magnetic field, and so on. The point is that an electromagnetic wave is its own matter.
What Kind of Wave is This?
- Vibrating electric and magnetic fields are perpendicular to each other
- Travel outward from charge
Other Properties of an Electromagnetic Wave
- Vacuum - All EM waves travel at 300,000 km/s, or "The Speed of Light"
- Changes based on material it travels through
- Slowest in liquids and fastest in gases
Wavelength and Frequency
- Wavelength - measured same as any wave
- Frequency of Wave = Frequency of vibrating charge that produces wave
Interaction With Matter
- Can travel through matter, as well as space
- When an object is encountered, the vibrating electric and magnetic fields exert forces
- Forces are exerted on charged particles and magnetic materials that compose the object
- Particles in object gain energy from this interaction
- For ex., electromagnetic waves from sun make sidewalk hot
Relationship Between Electromagnetic Waves and Particles
- Particle is a piece of matter
- Electrons, or particles, create an interference pattern - It was originally thought only waves could do this
- In this way, electrons behave like waves
- Particles don't move as a wave
- Photon is just a massless bundle of energy that acts as a particle
Types of Electromagnetic Waves
Real-World Uses of Electromagnetic Waves
- Radio - listen to radio
- Microwave - Microwave mac & cheese
- Infrared - TV remote control
- Visible Light - You can't see without it
- UV - Vitamin D (bone health)
- X-Ray - x-ray broken bones
- Gamma - Cancer treatment