Lecture 4 Electric Charge Coulomb’s Law Gecko Electric charge.
Chapter 12 Sections 1 & 2. Electric and Magnetic Fields An electric charge is surrounded by an...
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Transcript of Chapter 12 Sections 1 & 2. Electric and Magnetic Fields An electric charge is surrounded by an...
ELECTROMAGNETIC WAVES AND THEELECTROMAGNETIC SPECTRUM
Chapter 12 Sections 1 & 2
Electric and Magnetic Fields
An electric charge is surrounded by an electric field
A moving electric charge produces a magnetic field
A moving magnetic field produces an electric field
Electromagnetic Waves
When an electric charge vibrates, its electric field changes, creating a changing magnetic field
The changing magnetic field produces a changing electric field and the process repeats
Electromagnetic Waves
The pattern of changing fields produces an electromagnetic wave
Electromagnetic waves are transverse waves with specific wavelengths and frequencies
Electromagnetic Waves
All Electromagnetic Waves travel at the “speed of light”
3 x 108 m/s
When an EM wave encounters an object, its fields exert forces on that object
Waves and Particles Electromagnetic waves can behave as
a particle, called a photon, whose energy depends on the frequency of the waves Photons are said to
have a dual nature – they can behave like waves and particles
The Electromagnetic Spectrum Electromagnetic waves are categorized by how they interact with matter. This depends on their frequency.
The entire range of EM frequencies is the Electromagnetic Spectrum.
Radio Waves
Radio waves are electromagnetic waves with the longest wavelengths (longer than 1mm)
They are used in communications, radar, microwaves, and MRIs
Microwaves
Microwaves are radio waves with wavelengths less than 30 cm but longer than 1mm
Cell phones and satellites use microwaves
• Microwaves in microwave ovens cause water molecules to rotate, heating your food
Infrared Waves
Infrared waves have wavelengths between 1mm and 750 billionths of a meter
Thermal energy travels in infrared waves
• Remote controls and CD-ROM drives also use infrared waves
Visible Light Visible light has wavelengths
ranging from 750 billionths to 400 billionths of a meter
The spectrum of visible light ranges from red (longest ) to violet (shortest )
Visible Light
(ROYGBIV)
Ultraviolet Waves
Ultraviolet, or UV waves, have wavelengths of 400 billionths to 10 billionths of a meter
UV waves can cause skin damage such as sunburn, wrinkling, and cancer
Ultraviolet Light
UV light enables your body to make vitamin D
UV waves can kill bacteria by damaging its DNA
X-Rays
X-rays have wavelengths between ten billionths of a meter and ten trillionths of a meter
X rays are commonly used by doctors
and dentists
Gamma Rays
Gamma waves have wavelengths shorter than 10 trillionths of a meter
Gamma rays are produced by radioactive decay or other subatomic processes