Electromagnetic radiation

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16 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

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Radiant Energy
























particles or waves of energy emitted


Electromagnetic radiation



energy released from
all objects



Nuclear radiation



energy released when a
nucleus of an atom changes




Radiation


Electromagnetic Radiation


Energy emitted from all atoms when
electrons move to different energy levels
in an atom


Energy is not matter it is a wave

Types of Electromagnetic Radiation

Ionizing


high energy radiation that

produces ions


(alpha, beta, gamma)


Non
-
ionizing radiation


low energy radiation that

doesn’t produce ions

Visible Spectrum

Electromagnetic radiation moves in waves

Waves can be described in terms of four characteristics


Amplitude


Wavelength


Frequency


speed

Wavelength

is distance between crests:




measured in m, cm, mm,

m, nm, etc.

Amplitude

is the height of wave: Intensity of light depends on amplitude


measured in m, cm, mm,

m, nm, etc.



Frequency

is how fast the wave oscillates up and down:





measured in cycles/sec. Also called a Hertz (Hz): 1/sec or sec
-
1



Speed

is the speed of light: 3.00 X 10
8

m/s c

Calculate



Green light has a wavelength of 570 nm.
What is it’s frequency?



What is the color of light that has a
frequency of 4.7 x 10
14

1/sec?

(look in book for color)

Energy, frequency and wavelength


are related


E= h




h= Planck’s constant


6.6262 X 10
-
34
Js


Calculate



A certain violet light has a wavelength
of 413nm. What is the frequency of the
light? What is the energy of the light?




㴠振

†††

㴠振


Convert nm to m




=
3.00X 10
8
m/s

= 7.26 X 10
14

1/s


413 X 10
-
9
m

E= h




E=(6.6262 X 10
-
34

Js)(7.26 X 10
14
1/s)



= 4.81 X 10
-
19
J

Light


Is a form of electromagnetic radiation


Has dual properties


Behaves like a
wave
. Moves through space
in waves


Behaves like a stream of
particles

called
photons

Light is

quantized


has a specific energy

Wave nature of light

Oscillating electromagnetic fields

Nuclear binding energy


E=mc
2


Mass is converted to energy

Mass proton=1.0078 amu

Mass of neutron=1.0087 amu

1J=1 kg m
2
/sec
2

1 amu=1.66 x 10
-
27

kg



Electromagnetic radiation has energy