What is the value of Planck's constant?

Planck's constant is a fundamental physical constant that plays a crucial role in quantum mechanics. The correct value of Planck's constant is 6.626 x 10^-34 J x s, which indicates that it is measured in joules times seconds. This unit reflects the relationship between energy and frequency, where energy (measured in joules) is related to the frequency of a photon (the number of cycles per second) through this constant.

Planck's constant essentially quantifies the size of the quantum of action, which is pivotal when discussing phenomena such as photons, where it helps determine the energy of a photon based on its frequency using the equation E = hν, where E is energy, h is Planck’s constant, and ν (nu) is the frequency.

The other choices present measurements that do not accurately convey the nature of Planck's constant. For example, using newtons times meters or watts times seconds doesn't represent the fundamental concept that Planck's constant encapsulates in quantum theory. The use of specific units is essential for accurately conveying physical ideas, and in the case of Planck's constant, joules times seconds is the correct and meaningful unit.