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Quantum Theory:


    1.    Explain what is meant by a quantum of energy.

    2.    Relate the energy of radiation to its frequency.

Key Terms:

    quantum    Planck's constant    photoelectric effect    photon

Web Resources:



Plank's Theory:

Plank's theory states that each element can only absorb a certain amount of energy (quantum) therefore it can only emit a limited amount of energy.  Each element absorbs energy only when the quantum is reached.  This was further explained by the equation:

                            E = hv        (h = 6.6262 x 10-34 plank's constant)

Plank used this concept to describe why certain elements give of different color lights emit different colors.  It can also be used to determine the compositions of different stars in the galaxy.

Photoelectric Effect:

Einstein called the quantum packets of energy photons.  Each photon caries the exact amount of energy that the atom absorbed.

The Photon has a dual nature.  One part light and mass.  This dual nature allows this the photon to behave as a particle and collide with the electron.


When light energy comes in contact with certain metals it can be used to eject electrons from the surface of the metals.  Since atoms do not give up their electrons until reaching their quantum energy requirements, there is a minimum light requirement.  Red is incapable of causing a photoelectric effect regardless of the intensity.  Violet on the other hand, will power a device even at low intensities.

The atom is the source of all light.

When an atom absorbs electricity its electrons (e-) become excited
The excited e- jumps to higher energy orbits
As the excited e- looses energy, it falls back to its original orbit and releases a photon.
A photon is a tiny packet or bundle of energy that contains the exact amount of energy that the atom absorbed.




Last modified: October 03, 2002