ELECTROMAGNETIC RADIATION

ELECTROMAGNETIC RADIATION IS A FORM OF ENERGY. IT CAN BEHAVE AS PARTICLES OR WAVES. SOMETIMES, WE USE THE TERM “LIGHT” WHEN WE ARE TALKING ABOUT ELECTROMAGNETIC RADIATION. LIGHT IS GENERALLY USED TO DESCRIBE THE ELECTROMAGENTIC RADIATION THAT THE HUMAN EYE CAN SEE. THE TYPE OF RADIATION IS CHARACTERIZED BY ITS WAVELENGTH.

Wavelength = l Frequency = n = c / l

VISIBLE LIGHT GOES FROM 400 TO 700 NANOMETERS (nm) 1 nm = 10-9 meter

THE HUMAN EYE IS VERY LIMITED IN WHAT IT CAN SEE. WE ONLY SEE THIS NARROW LITTLE BAND OF THE ELECTROMAGNETIC SPECTRUM. 400 TO 700 nm

WHAT DOES THIS MEAN FOR SCIENTISTS? THE ENERGY OF ELECTROMAGENTIC RADIATION IS INVERSELY PROPORTIONAL TO ITS WAVELENGTH. THE ENERGY OF A PHOTON IS GIVEN BY: E = hn = hc / l where h = boltzman constant THIS MEANS THAT THE SHORTER THE WAVELENGTH, THE MORE ENERGETIC THE RADIATION. WHAT DOES THIS MEAN FOR SCIENTISTS?

IMAGINE IF WE WERE TRYING TO LOOK AT A BASEBALL GAME, AND VISIBLE LIGHT WOULD ALLOW US TO SEE ONLY A VERY SMALL SECTION OF THE BALL PARK. IT WOULD BE VERY DIFFICULT TO TELL MUCH ABOUT THE GAME OF BASEBALL.

IF OTHER WAVELENGTHS WOULD ALLOW US TO SEE OTHER SECTIONS, WE COULD PUT THE INFORMATION TOGETHER TO TELL WHAT A BALLPARK LOOKED LIKE.

DIFFERENT EVENTS INVOLVE DIFFERENT ENERGIES. IF SCIENTISTS CAN SEE AT DIFFERENT WAVELENGTHS IN ADDITION TO VISIBLE LIGHT, THEY CAN LEARN A GREAT DEAL MORE ABOUT THE NATURE OF THE UNIVERSE. EXAMPLES: SUPER NOVA INVOLVE VERY HIGH ENERGIES – THESE CAN RELEASE GAMMA RAYS. DEATHS OF RED GIANTS AND THE PLANETARY NEBULA THAT RESULT CAN RESULT IN RELEASE OF X-RAYS.

LOW TEMPERATURE OBJECTS SUCH AS BROWN DWARF STARS COULD BE SEEN WITH INFRARED RADIATION. THE BACKGROUND RADIATION FROM THE BIG BANG HAS RED-SHIFTED TO MICROWAVE RADIATION. RADIO WAVELENGTH RADIATION WOULD BE EMITTED AS THERMAL RADIATION FROM PLANETS AND FROM RAPID ROTATION OF NEUTRON STARS.