1. Electromagnetic Waves
Chapter 15
Section 1 and Section 2

2. Electromagnetic Waves
Waves cause something to vibrate
Electromagnetic waves are produced when electric charges vibrate
The vibrating electric charge is surrounded by changing electric and magnetic fields
Unlike Mechanical waves, they travel through both space and matter
Travel at 300,000 km/s in space
Travel slower in matter
Energy from a electromagnetic wave is radiant energy

3. Anatomy of an Electromagnetic Wave
Is a combination of a electric field and a magnetic field
They two field from waves at right angles to the direction the wave travels
Transverse wave

4. Electromagnetic Waves as Particles
Electromagnetic waves can behave has both waves and particles
The particles are photons
Photons are localized packets of energy that can behave like particles
In this modern view, they define light as a collection of one or more photons propagating through space as electromagnetic waves
Because electromagnetic waves behave as particles, the energy of a wave is measure using frequency.

5. The Electromagnetic Spectrum
Electromagnetic waves can have a wide range of frequencies
The entire range is known as the electromagnetic spectrum

6. Radio waves
A radio wave does not have rarefactions and compressions so it cannot be heard
Low frequency
High (Long) Wavelength
Can be as short as a few mm to as long as several kilometers
Shorter wavelength radio waves are microwaves
Microwaves are used to heat food by exciting water molecules
The vibration of water molecules causes friction and generates thermal energy

7. Other Uses of Radio Waves
RADAR
Stands for RAdio Detecting And Ranging
Measure the time required for waves to bounce off an object and return
Used by law enforcement to determine vehicle speed, track an aircraft, watercraft, or spacecraft.
MRI
Allows doctors to produce pictures of the inside of the body painlessly

8. Infrared (IR) Waves
Wavelength between 1 mm and 750 billionths of a meter
Thermal energy is transmitted as infrared waves
Used in
Remote controls
Computers to read CDs and DVDs
All objects emit IR Waves

9. Visible Light Can be detected with the eye
Wavelengths from 750 billionths to 400 billionths of a meter

10. Ultraviolet Waves
Range from 400 billionths to 10 billionths of 10 billionths of a meter
Can enter skin cells
Can cause skin damage and cancer
Most UV radiation that reaches Earth is longer wavelength
Shorter wavelengths cause sun-burn
Some exposure is necessary to help skin make Vitamin D

11. X-Ray and Gamma Rays Shortest wavelengths Most energetic
Doctors and dentists uses low does to get images of internal organs, bones, and teeth
Really short X-rays are Gamma Rays
Can penetrate lead by a several centimeters
Can cause damage to living cells and tissues