Why Do Units on Plank's Constant Include Mass, Length, and Time?

In summary, the units of Plank's constant are m^2 * kg / s because when units were first devised, the relationship between length, mass, and time was not fully understood. Planck's constant can also be defined as the ratio of energy to frequency, demonstrating the connection between energy and units of mass, length, and time.
  • #1
nhmllr
185
1
The units on Plank's constant is m^2 * kg / s
I'm new to all of this stuff so... Why?
 
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  • #2
Because when people devised units, they didn't realize that there are equivalence relationships between length, mass and time.

But to more directly answer your question, Planck's constant really has units of (energy)(time). To see this, note that Planck's constant can be defined by the ratio of the energy and frequency of a photon :

[tex] h= \frac{E}{\nu}.[/tex]

In order to explain the relationship of energy to units of mass, length and time, you might want to consider basic formulae from classical mechanics.
 

1. What is Plank's constant?

Plank's constant, denoted as h, is a fundamental physical constant that is used to describe the relationship between the energy of a photon and its frequency. It was first introduced by Max Planck in 1900.

2. What are the units of Plank's constant?

The units of Plank's constant are Joule seconds (J·s) in the International System of Units (SI). It can also be expressed in electron volts seconds (eV·s) in the atomic unit system.

3. How is Plank's constant measured?

Plank's constant is a universal constant and is not measured directly. Instead, it is derived through experiments and theoretical calculations, such as the photoelectric effect and blackbody radiation.

4. Why is Plank's constant important?

Plank's constant plays a crucial role in quantum mechanics and is used in many equations to describe the behavior of particles at the atomic and subatomic levels. It is also used in various fields of physics, such as electronics, optics, and thermodynamics.

5. Can Plank's constant change?

No, Plank's constant is a fundamental constant and is believed to be a constant value in nature. It has been experimentally verified to be the same value throughout different points in time and space. However, there are some theories that suggest it may vary in extreme conditions, but this has not been proven.

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