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I. Waves & Particles
Electrons in Atoms
A. Waves
Wavelength () - length of 1 complete wave
Frequency () - # of waves that pass a point during a certain time period hertz (Hz) = 1/s
Amplitude (A) - distance from the origin to the trough or crest
A. Waves
Agreater
amplitude(intensity)
greater frequency
(color)
crest
origin
trough
A
B. EM Spectrum
LOW
ENERGY
HIGH
ENERGY
B. EM Spectrum
HIGH
ENERGY
R O Y G. B I V
red orange yellow green blue indigo violet
B. EM Spectrum
Frequency & wavelength are inversely proportional
c = c: speed of light (3.00 x 108 m/s): wavelength (m, nm, etc.): frequency (Hz)
B. EM Spectrum
GIVEN:
= ?
= 434 nm = 4.34 x 10-7 m c = 3.00 x 108m/s
WORK: = c
= 3.00 x 108 m/s
4.34x 10-7 m
= 6.91 x 1014 Hz
EX: Find the frequency of a photon with a wavelength of 434 nm.
B. EM Spectrum
Energy and frequency are directly related
E = h E: Energy (joules, j)h: Planck’s constant(6.626 x 10-34 m2kg/s): frequency (Hz)
B. EM Spectrum
GIVEN:
E = ?h = 6.626 x 10-34
m2kg/s
= 6.38 x 1014 Hz
WORK:E = h E = 6.626 x 10-34 m2kg/s x
6.38 x 1014 Hz
E = 4.23 x 10-21 J
EX: Find the energy of a photon with a frequency of 6.38 x 1014 Hz.
B. EM Spectrum
GIVEN:
E = ?h = 6.626 x 10-34
m2kg/s
= ?C= 3.00x108m/s = 4.6 nm
= 4.6 x 10-9m
WORK: = C/ =(3.00x108m/s)/ (4.6x10-9m) =1.4 x 1016/sE=h E= 6.626 x 10-34 m2kg/s x 1.4 x 1017/s
E = 9.3 x 10-18 j
EX: Find the energy of a photon with a wavelength of 4.6 nm.
C. Quantum Theory
Planck (1900)
Observed - emission of light from hot objects
Concluded - energy is emitted in small, specific amounts (quanta)
Quantum - minimum amount
of energy to change
C. Quantum Theory
Planck (1900)
vs.
Newtonian Theory Quantum Theory
C. Quantum Theory
Einstein (1905)
Observed - photoelectric effect
C. Quantum Theory
Einstein (1905)
Concluded - light has properties of both waves and particles
“wave-particle duality”
Photon - particle of light that carries a quantum of energy