The tool that was used to "dissect" or probe the atom was electromagnetic radiation (EMR), form of energy thought (remember our time frame in history) to consist entirely of waves oscillating in electric and magnetic force fields positioned at right angles with respect to each other.
To understand EMR, terms associated with wave motion must be defined and understood.
wavelength (lambda, ), the distance between two adjacent points that are "in phase."
, measured in length units: m, cm, nm, å ...
1 nm = 1x10-9 m, 1 angstrom (å) = 1x10-10 m, 1 nm = 10 å
frequency ( f or v ), the number of waves passing a given fixed point per unit time.
velocity (v or c, for all forms of EMR), the distance traveled by a fixed point on a wave per unit time.
Putting wavelength, frequency, and velocity together
(m) x ( ) = m/s
v = c
= wavelength in m
v = frequency in
c = speed of light
Since c is a constant, v & are inversely proportional
Max Planck (1901) was studying radiation emitted by solid bodies heated to incandescence. Planck found that his results could not be explained in terms of current nineteenth century physics. Planck discovered that energy can only be gained or lost in integer multiples (n) of h v, h is called Planck's constant (6.626x10-34 J s) and v the frequency.
E = nh v
E = Energy of quanta
n = integer
h = Planck's constant
v = frequency of EMR
Planck's results showed that energy was quantized. Planck called each of the small "packets" of energy a quantum (singular, noun). Energy can only be transferred in whole quanta, therefore energy seems to have particulate properties.
Albert Einstein (1905) showed that electromagnetic radiation is quantized. Electromagnetic radiation can be viewed as a stream of "particles", Planck called these particles quanta, Einstein called the stream of "particles" photons (the term photon was "coined" by G.N. Lewis)
Ephoton = hv =
The energy of the photon found from the above equation could be then plugged into Einstein's famous equation E = mc2. Solve for m and obtain:
Einstein had theoretically proven that a photon of light has mass or mass energy. American physicist Arthur Compton performed experiments in 1922 proving Einstein's relationship above. This was the beginning of physics for the twentieth century. The new physics was later called quantum physics.
Summary of Planck and Einstein's work
This page was made by Erik Epp.