ELECTROMAGNETIC RADIATION
• Radiant energy that exhibits wavelength-like
behavior and travels through space at the
speed of light in a vacuum.
• A wave transmits energy.
PROPERTIES OF WAVES
Waves have 3 primary characteristics:
1. Wavelength: distance between two peaks in a
wave.
2. Frequency: number of waves per second that
pass a given point in space.
3. Speed: speed of light is 2.9979  108 m/s.
RELATIONSHIP BETWEEN WAVELENGTH AND
FREQUENCY
c=
 = frequency (s1, Hz)
 = wavelength (m)
c = speed of light (m/s)
 Wavelength is inversely related to frequency
WAVE EQUATION EXAMPLES
1. Calculate the frequency of a wave traveling through
space with a wavelength of 1.96 x 10-6 m.
2. Calculate the wavelength of the yellow light emitted by
a sodium lamp if the frequency of the radiation is
5.09X1014 Hz.
ELECTROMAGNETIC SPECTRUM
MAX PLANCK
• German physicist
• Energy is quantized
• It can only occur in
discrete units
(“packets”) called a
quantum.
PLANCK’S EQUATION
E = h =
hc

E = change in energy, in J
h = Planck’s constant, 6.626  1034 J s
 = frequency, in s1
 = wavelength, in m
EINSTEIN’S CONTRIBUTION
• Stated EMR can be viewed
as a stream of “particles”
called photons.
• Photon = a quantum of EMR
• Can use Planck’s equation to
find energy of photon
EXAMPLE:
1. What is the energy of a photon of radiation
with a frequency of 7.85 X 1013 s-1?
2. The microwaves emitted by a cell phone have
a wavelength of 2.35 X10-2 m. What is the
energy of a microwave photon?
WHAT IS SPECTROSCOPY?
• The science of analyzing matter using
electromagnetic emission or absorption
spectra.
• Used in many fields of science such as
astronomy or forensics.
ATOMIC EMISSION SPECTRUM
A characteristic set of colored lines that is
unique for each element (“fingerprint”)
Different # of electrons
Caused by the electrons releasing energy as they
go from the excited state back down to the
ground state
Each line corresponds to a specific photon of
light being emitted
EXCITED VS. GROUND STATE
Ground State: the lowest possible energy
of an atom described by quantum
mechanics
Excited State: electrons jump to higher
energy levels due to an input of energy
It takes a quantum of energy to jump
electron to the next higher energy level
WHAT PRODUCES AN EMISSION SPECTRUM?
When energy is added to an atom, it
causes the electrons to jump up to
higher energy levels (become “excited”).
They release energy when they return to
the ground state.