electromagnetic spectrum

  The electromagnetic spectrum is what scientists call the group of different types of radiation.  The waves in the spectrum are commmonly constructed from the longest and lowest in frequency, to the shortest and highest in frequency.  Radiation is energy that emits waves or particles.  Waves in the electromagnetic spectrum do not have to travel through a medium, instead, they are able to traverse through vacuums.

  All electromagnetic waves have four things in common: amplitude (intensity/brightness), wavelength (a length from crest to crest or trough to trough), velocity (speed), and frequency (number of waves per unit in time).  Waves in the spectrum are all transverse waves.

  The seven waves in the electromagnetic spectrum (in order from longest to shortest wavelength) are radio waves, microwaves, infrared waves, visible waves (light), ultraviolet waves, x-rays, and gamma-rays.

RADIO WAVES:

  Radio waves, which have the longest wavelengths in the electromagnetic spectrum, can vary in size from a football to much larger than earth.  Radio waves are primarily used for transmitting signals over a very long distance (more commonly known as long-distance communication).  By bouncing signals off of the ionosphere (layer in earth's atmostphere than contains electron-stripped atoms), the radio waves that are reflected can relay a signal over a huge distance.  However, interference is a common occurence when using radio waves.  Radio waves can travel through most materials, but the wave often slows down, decreasing the quality of the signal.  When the wave gets to a point where it is slowed down a significant amount, interference (static sound) is often heard.  Radio waves are also naturally emitted by things such as stars and gases found in space.

          wavelength = 8 x 10^6 - 3 x 10^0 m

          frequency   = 6 x 10^2 - 1 x 10^8 Hz

  Radio waves are used in our everyday lives to transfer information over a distance without the use of wires.  Listening to the radio, making a phone call, and watching television would not be possible if it weren't for the existence of radio waves.  The images and sound are bounced off of a broadcasting tower and reflected back to us, which allows to watch or listen to the signal by use of the transmission of signals in the form of radio waves.  Radio waves are also heavily relied upon to determine location electronically.  When sent out, they bounce off objects, and reflect back to their origin.  The navy utilizes this phenomenon through the use of radar.  When searching for another ship, radar radio waves are sent out in all directions, and when they come in contact with another ship, they relay the location back to the navy ship, revealing the other ship's exact location.



waves being transmitted



VISIBLE (LIGHT) WAVES:

  The portion of electromagnetic radiation that the human eye can detect (the smallest portion on the spectrum) is referred to as light.  When visible waves are emitted, the retina in a human (or animal's) eye receives and deciphers the light.  The light waves cause a chemical change in our retina, allowing us to see, while light waves that strike materials often cause temperature and electrical changes.  Only visible waves can be received by the retina because other waves in the spectrum have wavelengths either too big or too small.  When light travels through the prism of the retina, the wavelengths seperate into their distinct color of the rainbow (determined by size).  Light waves can be created by an object getting substantially heated, or having a specific chemical or electrical reaction.  Light is able to pass through many materials, such as glass. 

          wavelength = 4 x 10^-7 - 1.5 x 10^-7 m

          frequency   = 4 x 10^14 Hz - 7.5 x 10^14 Hz

  Visible waves are needed for a human to function in everyday life.  Without them, we would not be able to see anything.  Over time, our retinas have developed in order to tune in to certain wave frequences (visible waves) caused by the light emitted from the sun.  Visible waves are also used to make CDs and DVDs.  Microscopic pits are carved into the disc, and when light from the CD/DVD reader is reflected upon the surface, the pattern is deciphered into sound, images, or data.



retina receiving light of the stop sign



bibliography:

pictures:

 http://www.nasa.gov/images/content/201940main_SOMD_Radar_xltn.jpg

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5PWM8wIAZtQS9ekc4vxmwdJTcGI5iR6ff48PM64X8ObtwE2JblGO_-LGA7I_U8nCQoBLpNK47fGW83s2dav9reHgsxvfZ-SLXUXdG3ow8RO883keA10t2WRtL3vvB2s1mimAiWWFuU6Q/s1600/retina.gif

information:

http://missionscience.nasa.gov/ems/05_radiowaves.html

http://school.discoveryeducation.com/lessonplans/interact/electromagneticspectrum.html

http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

http://panasonic.net/pcc/support/tel/cdl_noise.htm

http://www.darvill.clara.net/emag/emagvis.htm

http://missionscience.nasa.gov/ems/09_visiblelight.html

http://school.discoveryeducation.com/lessonplans/interact/electromagneticspectrum.html