Transcript Mechanisms for the Radiation of Electromagnetic Waves

HowRadiateEMWaves.ppt
How do objects emit em waves?
Kinetic Theory
The temperature of an object is determined by the energy of the motion
(called kinetic energy) of the objects in the system
T is proportional to KE
Implication: The higher the kinetic energy of the object, the higher it’s
temperature
KE = ½ m v2
How do objects emit em waves?
When an charged object accelerates, it must change it’s energy if the acceleration
causes a change in speed.
If the acceleration of the charged object results in a loss of energy of the object,
that energy will be released in the form of electromagnetic energy.
How do objects emit em waves?
Peculiar discovery of Einstein
Electromagnetic energy is not released in the form of an electromagnetic “wave”
but rather is released in the form of an electromagnetic “particle” called a photon.
The energy of motion of this photon is not the usual kinetic energy, but the energy
of the photon is given by
E=hf
Where h is called Planck’s constant and f is the frequency of the EM wave.
h = 6.6 x 10-34 J sec
Photon
How do objects emit em waves?
Peculiar discovery of Einstein
Electromagnetic phenomena have characteristics of both a wave and a particle (?).
THEREFORE:
A photon has all of the characteristics discussed in wave phenomena, but they also
have the characteristics of a particle.
The any decrease in energy experienced by a charged particle when it accelerates
is equal to the energy carried by the photon. Since the energy of the photon is
related to the photon’s frequency, one can calculate the frequency of the photon on
the basis of the amount of energy lost by the particle. In the visible portion of the
electromagnetic spectrum, the frequency can be used to identify the color
associated with the emitted photon.
How do objects emit em waves?
Kinetic Theory
Conservation of Energy
Einstein
The Photoelectric Effect
T related to KE
ΔEcharge = Ephoton
Ephoton = hf
The Temperature of a star is related to the frequency of radiated EM
waves. The color of the star provides information about it’s temperature.
How do objects emit em waves?
When the particles in the solid, liquid, or gas accelerate, they will
produce EM waves.
Mechanisms:
Particle vibrations
Particle rotations
Electron transitions through chemical bonds
Particle-particle collisions
Electron orbit to orbit transitions in atoms
Gravitational Forces
How do objects emit em waves?
When the particles in the solid, liquid, or gas accelerate, they will
produce EM waves.
Mechanisms (primarily):
Particle vibrations (solids, liquids, gasses)
Particle rotations (gasses)
Electron transitions through chemical bonds (solids, liquids)
Particle-particle collisions (gasses)
Electron orbit to orbit transitions in atoms (gasses)
Gravitational Forces
Applicable to the study of stars (gaseous objects)
How do objects emit em waves?
When the particles in the solid, liquid, or gas accelerate, they will
produce EM waves.
Mechanisms (primarily):
Particle vibrations (solids, liquids, gasses)
Particle rotations (gasses)
Electron transitions through chemical bonds (solids, liquids)
Particle-particle collisions (gasses)
Electron orbit to orbit transitions in atoms (gasses)
Gravitational Forces
Applicable to the study of stars (gaseous objects)
Applicable to the study of massive objects