Waves

1. electromagnetic wave (EM)--- transfers electrical and magnetic energy

An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light.

· light and sound combinations---sometimes one sees the light before hearing the sound because light travels faster than sound (planes, rockets, fireworks, explosion, thunder/lightning)

2. electromagnetic radiation---the energy that is transferred through space by electromagnetic waves

· radiation is energy that travels and spreads out as it goes

3. electromagnetic spectrum (EM spectrum)--- the complete range of electromagnetic waves placed in order of increasing frequency

· of radio waves, infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays

· EM spectrum has benefited the study of astronomy

· Only extremely hot objects or particles moving at very high velocities can create high-energy radiation like X-rays and gamma-rays.

· Hotter, more energetic objects and events create higher energy radiation than cool objects.

Electromagnetic Spectrum

long ← wavelength → short

low ← frequency → high

lower ← energy → higher

EM Waves and Their Characteristics

Wave Type	Description	Effects on Living Things/Uses by People
radio waves	longest wavelengths, lowest energy	s transmits radio and television signals s used in cell phones and radar s TV and FM radio use shorter wavelengths than AM radio s GPS (global positioning system) s Emitted by stars and gases in space
Microwaves	Shorter wavelengths and higher frequency than radio waves	s Used to cook in microwave ovens s Used to send cell phone signals s Radar also used these signals (weather Doppler effect radar and police radar) s used by astronomers to learn about the structure of nearby galaxies and our own Milky Way
Infrared (IR) light	---fairly long (about the length of a fingernail), low-frequency waves ---heat from the sun travels to Earth in this form	s Used by some insects (IR-sensitive beetles) and snakes (pythons, pit vipers) s Felt as heat by humans s Night vision goggles use infrared sensors s Infrared cameras used by firefighters to locate fire victims s heat lamps---used to keep food warm and to heat bathrooms quickly s infrared heat lamps can be used by pet owners to help their reptiles maintain internal (core) body heat s satellites in space use infrared cameras to study the growth of plants and motions of clouds s in space, IR light maps the dust between stars
Visible light	---includes the visible spectrum (rainbow): red, orange, yellow, green, blue, indigo, and violet ---longest wavelength of visible light is red, and the shortest is violet	s The only part of the EM spectrum humans can see s Nearly 90% of the light energy used by plants for photosynthesis comes from red light s Light that comes from a lamp in your house s Emitted by stars
Ultraviolet (UV) light	---higher energy and higher frequency than visible light ---can make certain minerals glow	s Not visible to humans, but used by bees and some other insects to see s Prolonged exposure can damage cells s Causes skin to make vitamin D s Can burn skin or lead to skin cancer in humans and some other animals s Photosynthesis s Greenhouse gases (CO₂, CH₄)—short wave UV radiation is allowed to enter the atmosphere but long wave infrared radiation is trapped by the gases which causes the Earth to warm (greenhouse effect) s Stars and other "hot" objects in space emit UV radiation.
X-rays	---high-energy, high-frequency ---can travel through soft tissue, such as skin and muscle, but not through hard bone	s Repeated exposure can damage cells s Used for medical imaging (bones, teeth) s Used in security checks to find hidden objects s by engineers to check for cracks in steel or concrete s used to check the quality of joints in oil and gas pipelines s Hot gases in the Universe also emit X-rays
Gamma rays	---highest energy, highest frequency ---produced by the sun and other stars	s Very damaging to cells s Used to sterilize medical equipment by killing any germs on the equipment s some objects in space give off or emit gamma rays---gamma ray telescopes that detect them must orbit above Earth’s atmosphere