ELECTROMAGNETIC RADIATION - PowerPoint PPT Presentation

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ELECTROMAGNETIC RADIATION

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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 ... – PowerPoint PPT presentation

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Title: ELECTROMAGNETIC RADIATION


1
ELECTROMAGNETIC RADIATION
2
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.
3
Wavelength l Frequency n c / l
4
VISIBLE LIGHT GOES FROM 400 TO 700 NANOMETERS
(nm) 1 nm 10-9 meter
5
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
6
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?
7
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.
8
IF OTHER WAVELENGTHS WOULD ALLOW US TO SEE OTHER
SECTIONS, WE COULD PUT THE INFORMATION TOGETHER
TO TELL WHAT A BALLPARK LOOKED LIKE.
9
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.
10
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.
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