In the late 1900s, a German physicist named Max Planck
(1858-1947) had discovered an empirical formula that fit the blackbody spectra,
which is…
E = spectral radiance
C1 & C2 =
constants
Lambda = wavelength
T = temperature in Kelvin
To evaluate the
constants, Planck considered a cavity of temperature filled with blackbody
radiation. (Can be thought as a hot oven filled with standing waves of
electromagnetic radiation). Planck
attempts to extend the permitted wavelength forever to increasingly shorter
wavelengths, such as 2L, L, 2L/3, etc.
Each permitted wavelength should and could only receive an
amount of energy equation to kT, a direct similarity to ideal gas law. This is
considered an “ultraviolet catastrophe” because the infinite number of
infinitesimally short wavelengths implied that an unlimited amount of blackbody
radiation energy was contained in the oven.
Planck attempts to circumvent this problem by using a clever
mathematical trick that involves assuming that a standing electromagnetic wave
of wavelength and frequency could not acquire just an arbitrary amount of
energy, but instead the wave could have only specific energy values that were
integral multiples of minimum wave energy, known as quantum of energy. So given the assumption of quantized wave
energy with a minimum energy proportion to the frequency of the wave, the
ultraviolet catastrophe can be avoided.
Planck hopes that the constant "h" will be 0, hoping
that an artificial constant should not remain as his result.
Planck stratagem worked, but his formula only worked if the
constant “h” is a certain value.
Therefore, the value
became known as Planck’s constant, which is 6.26E-34 J/s.
