Question

The numerical value of Planck’s constant is
A.\[6.6 \times {10^{ -20}}{\text{Jsec}}\]
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:Planck theory explains the particle nature of light. He explained the concept of quantum or photon and energy of quantum to be directly proportional to its frequency associated.

Complete answer:
Light has dual nature namely both wave nature and particle nature. Properties of light like interference and diffraction can only be explained if considered wave nature of light. On the other hand, properties of light like photoelectric effect and black body radiation can only be explained if considering the particle nature of light.
Black body radiation phenomenon was first properly explained by Max Planck. Through various experiments, he concluded that the ideal body which absorbs and emits radiation of all possible frequencies is known as black body and the radiation associated with the black body is known as black body radiation. He also concluded that the radiation emit or absorb by a body is not continuous in terms of frequency or wavelength which means a real body does not emit or absorb radiation of all possible frequencies but rather radiation emit or absorb by a real body is in discrete quantity or in fixed packets. He defined quantum as the smallest quantity or packet of energy which can be absorbed or emitted by the body in the form of electromagnetic radiation. Also, the energy of this packet or energy of quantum is directly proportional to its frequency. The equation for the energy associated with the photon in terms of frequency can be represented as: \[{\text{E}} = {\text{h}}\nu \] where E is the energy of quantum, \[\nu \] is the frequency of quantum and h is the proportionality constant known as Planck’s constant and has the value \[6.6 \times {10^{ - 34}}{\text{Jsec}}\] . This theory of Max Planck can explain the distribution of intensity in the radiation as a function of frequency or wavelength for a black body at different temperatures.

Thus, the correct option is B.
Note:
Phenomenon like black body radiation, photoelectric effect, variation of heat capacity as a function of temperature for solid and line spectra of atoms proves the particle nature of light. The unit of Planck’s constant is \[{\text{Jsec}}\] .