Chapter 12 Sections 1 & 2

Warm Up: How is an electromagnetic wave created? How is an electromagnetic wave different from a mechanical wave?

Warm Up: How is an electromagnetic wave created? An electromagnetic wave is made from vibrating electric charges How is an electromagnetic wave different from a mechanical wave? An electromagnetic wave does not need matter to travel like a mechanical wave does

Electric and Magnetic Fields Review  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 10 8 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