Question

The numerical value of planck’s constant is __________ .
A: $ 6.6 \times {10^{ - 19}}{\text{Jsec}} $
B: $ 6.6 \times {10^{ - 34}}{\text{Jsec}} $
C: $ 6.6 \times {10^{ - 25}}{\text{Jsec}} $
D: $ 6.6 \times {10^{ - 50}}{\text{Jsec}} $

Answer 1

Hint: In quantum physics , the energy of electromagnetic radiation is restricted to indivisible packets called photons . Every photon has an energy $ {E_f} $ , $ f $ being the frequency of the radiation , and $ h $ a universal constant recognized by Max Planck.

Planck's constant as the name goes was first introduced by my great physicist Max Planck in order to explain blackbody radiation which was a great mystery those days.
Planck hypothesized​ that energy emitted by a blackbody is always in the integer multiple of quanta of energy. Planck hypothesized this just to match black body radiation spectrum.
Einstein used this hypothesis to explain the photoelectric effect.
 $ \
  {\text{As einstein thesis,}} \\
  {{E = m}}{{\text{c}}^2} \\
  {\text{However when we are dealing with the photons of light}} \\
  {{E}} \propto {\text{c}} \\
  {{E}} \propto \dfrac{1}{\lambda } \\
  {{E = h}}\dfrac{c}{\lambda } \\
  {\text{here,}} \\
  {\text{h = Planck's constant}} \\
  {\text{c = speed of light}} \\
 \lambda = {\text{Wavelength of light}} \\
  {\text{h = 6}}{\text{.636}} \times {\text{1}}{{\text{0}}^{ - 34}}{\text{J sec}} \\
\ $
Correct Option is B.

Additional Information:
The physics of classical many-particle systems then is a very convenient space to use when describing such systems where you have an axis for every direction of ordinary 3d space for each particle but also an axis for every direction of momentum of each particle. It is described with systems with very many particles by following the evolution of the density of particles in this larger space. This larger space is called phase space and a well-known result from classical mechanics is that the classical equations of motion conserve the density in this space. So little volume-elements containing those particles in phase-space may change their shape and form, but they won’t change their size. The units of that phase-space volume are (Joules x second) to the power of $ {3^n} $ if you have n particles. So it is interpreted that the Planck’s constant to the power $ {3^n} $ as a fundamental unit of phase-space volume. It tells you something about the fundamental ‘graininess’ of nature. Planck’s constant itself does not explain this graininess, but quantum mechanics does and quantum mechanics relies heavily on Planck’s constant.

Note:
Energy, mass, momentum, time, distance, can all be defined in terms of a minimum measurable value. In these definitions, Planck’s constant puts a limit on how much you can know about the state of a particle.