What is Planck's constant and its approximate value?

Planck's constant is a fundamental quantity in quantum mechanics that relates the energy of a photon to the frequency of its associated electromagnetic wave. It is represented by the symbol h and plays a critical role in describing the quantization of energy levels in atoms and various phenomena such as the photoelectric effect. The approximate value of Planck's constant is 6.626 × 10^-34 Joule-seconds (Js). This small value reflects the quantum nature of particles at the microscopic level, indicating that the effects of quantum mechanics are typically observed at very small scales.

Understanding that Planck's constant serves as a bridge between the macroscopic and quantum worlds helps elucidate various physical processes, particularly in fields like spectroscopy, thermodynamics, and atomic physics. The other values listed in the options either pertain to different physical constants or are simply not relevant to quantum mechanics in the same context as Planck's constant.