Planck's Constant: Definition, Value, Units, Symbol and Facts - GeeksforGeeks (2024)

Planck’s Constant is one of the smallest constants used in physics. It is a fundamental constant in quantum mechanics which relates the energy of a photon to its frequency. Planck constant stands as one of the most elegant and pivotal values in the realm of physics, where constants shape the very essence of this physical world.

Further in this article, we will learn about its definition, who Max Planck was, explore methods for calculating its value in various units, its formula, dimension, and unit. We will look into what’s a Reduced Planck Constant and discuss the application of Planck’s constant across various scientific disciplines.

Planck's Constant: Definition, Value, Units, Symbol and Facts - GeeksforGeeks (1)

Table of Content

  • What is Planck Constant?
  • Value of Planck’s Constant
  • Planck Constant Formula
  • Experimental Determination of Planck’s Constant
  • Application of Planck’s Constant Different Fields

What is Planck Constant?

Planck’s constant, symbolized as ℎ, is a fundamental universal constant that defines the quantum nature of energy and relates the energy of a photon to its frequency, now known as the Planck-Einstein relation:

E = ℎf


  • E represents the energy of the light,
  • f is the frequency of the light, and
  • is referred to as the Planck constant.

Planck Constant tells us that energy exchanged at the quantum level occurs in some specific amount, known as quanta. The Planck’s constant says how much of that energy is in these quanta. One quanta is defined by the value of the Planck’s Constant value (we will learn about this value later in this article.)

Discovery of Planck Constant

German physicist Max Planck introduced the constant in 1900 when he was working on a formula to describe the distribution of radiation emitted by a blackbody, also known as blackbody radiation. This constant, now known as Planck’s constant, was crucial in resolving a problem known as the ultraviolet catastrophe, a point where classical physics failed to explain the observed physics.

Who is Max Planck?

Max Planck was a German physicist who pioneered the field of quantum theory. Planck’s most famous contribution was quantization of energy packets, which gave birth to the revolutionary idea that energy is not emitted or absorbed continuously but in discrete quantities. This constant came to be known as Planck’s constant and is now denoted by the symbol ‘ℎ’.

Value of Planck’s Constant

Planck’s constant, symbolized as ℎ, is a fundamental universal constant. From the data, its value is calculated and it came to be

6.62607015 × 10−34 Joule seconds

Value of Planck’s Constant in eV

Its value when calculated in terms of electron volts (eV) is very useful for quantum level calculations.

4.135667696 × 10−15 eV seconds

Planck Constant Formula

Its value can be easily calculated by putting values in the Planck-Einstein relation for the Photoelectric effect energy:

E = ℎf

Where E is the energy of the light, and f is the known frequency of the light.

Unit of Planck Constant

Planck’s constant is a very small value can be written in two formats:

Planck Constant = 6.62607015 × 10−34 Joule seconds

Here, 10-34 is a very small value, which is 1 in its 34th digit.

Planck Constant = 4.135667696 × 10−15 eV seconds

Here, 10-15 is a slightly larger but equivalently smaller quantity, which is 1 in its 15th digit.

Planck Constant Dimensions Formula

Dimension of Planck Constant is [ML2T-1]

Experimental Determination of Planck’s Constant

Experimental determination of Planck’s constant is done by the photoelectric effect. In this experiment, the energy of the electron emitted from a metal surface is precisely measured when light strikes it.

Also measuring the frequency of the incident light, a direct relationship can be found between the energy of the photons and the frequency of the light, that’s Planck’s constant. Accuracy of these experiments perfectly validate Max Planck’s theory, and in turns strengthening our understanding of the quantum world.

Reduced Planck Constant

Frequency is measured using hertz. A 360° cycle or one full Bohr introduced the quantity ℏ = ℎ/2π , Its value is 1.054571817×10−34 joule seconds, known as the reduced Planck constant, represents the quantum of angular momentum and more commonly used in modern physics.

Application of Planck’s Constant Different Fields

Planck’s constant plays a unique and foundational role across various scientific fields. Here’s a few perspectives that highlights its distinct and direct contributions:

In Quantum Mechanics, Planck’s constant (ℎ) acts as a bridge between the macroscopic and microscopic worlds, defining the granularity of energy at the quantum level. It’s the fundamental quantum unit that underpins numerous phenomena, making it unparalleled in its significance.

Planck’s Constant in Different Fields

There are various uses of Planck’s Costant in different fields of physics, some of these applicationa are listed as follows:

  • Black Body Radiation

Formula for spectral radiance B(v, T) is revolutionary, describing how objects emit light at different temperatures, and it is given by,

B(v, T) = 2ℎv3⁄c2 × 1 ⁄[eℎv/KT -1]

  • Photoelectric Effect

Planck-Einstein relation revolutionized our understanding of light’s interaction with matter, and it is given by,

E = ℎf

  • Atomic Structure

Within atomic models, Planck’s constant appears in equations describing the energy levels of electrons in orbits around the nucleus, and it is given by,

En = -ℎc0R ⁄ n2

  • Uncertainty Principle

The uncertainty principle embodies a fundamental limitation in measuring both the position and momentum of a particle simultaneously, and it is given by,

ΔxΔp ≥ ℏ⁄ 2

  • Matter-Wave Duality

The de Broglie wavelength equation relates a particle’s momentum to its associated wavelength, and it is given by,

λ= ℎ⁄p

Read More,

  • Planck’s Quantum Formula
  • Dual Nature of Light
  • DimensionalFormulaofPlanck’sConstant

Planck’s Constant FAQs

What is Planck’s Constant?

Planck’s constant, denoted as ℎ, is a fundamental constant in quantum mechanics that relates the amount of energy carried by photon to its frequency.

What is Planck’s Length, and What’s its Relation to Planck’s Constant?

Theoretically it is believed that Planck’s length is the smallest measurable length in the known universe, its value is roughly 1.616×10-35 meters, derived from Planck’s constant.

Can Planck’s Constant importance be Experimentally Demonstrated?

Yes, the Photoelectric effect effectively demonstrates the importance of Planck’s constant.

What is the Value of Planck’s Constant?

Its value is approximately 6.626×10−34 joule-seconds.

What is the Dimension of Planck’s Constant?

Dimension of Planck’s Constant is [ML2T-1].

What is the SI unit for Planck’s Constant?

SI unit of Planck’s Constant is Joule second.

What is Planck’s Constant in eV?

Value of Planck’s Contant is 4.135667696×10−15 eV seconds.

What is Reduced Planck Constant?

The reduced planks constant is ℏ=ℎ/2π.




Next Article

Constant in Maths

Please Login to comment...

Planck's Constant: Definition, Value, Units, Symbol and Facts - GeeksforGeeks (2024)


What is the value of Planck constant and symbol? ›

What Is the Value of Planck's Constant?
Value of h In SI unitsh = 6.6260715×10 -34 J.s
Value of h In Meter-Kilogram-Second(MKS) unitsh = 4.135667662×10-15 eV.s
Value of h in terms of Ep.tp2 pi

What is the Planck constant and its units? ›

The dimension of Planck's constant is the product of energy multiplied by time, a quantity called action. Planck's constant is often defined, therefore, as the elementary quantum of action. Its value in metre-kilogram-second units is defined as exactly 6.62607015 × 1034 joule second.

What is the unit of Planck's constant symbol? ›

It is the proportionality constant that relates the energy carried by a photon to its associated wave frequency. The numerical value of the Planck constant, symbol h, is defined to be exactly 6.626 070 15 × 1034 when expressed in the unit joule second, J s, or kg m2 s1.

What is the value of Planck's constant answer? ›

The value of Planck's constant is 6.63×10−34Js. The speed of light 3×1017nms−1.

What is Planck's constant used for? ›

Planck's constant is essential for understanding the motions of atoms and subatomic particles, as well as how quantum mechanics and modern electronics operate. At the time, existing formulas did not describe accurately the observed results for all temperatures.

What is the symbol of Planck length? ›

In physics, the Planck length, denoted ℓP, is a unit of length in the system of Planck units that was originally proposed by physicist Max Planck, equal to 1.616255(18)×10−35 m.

What are the units of the Planck function? ›

The units of the Planck function are erg/s/cm2/Angstrom/steradian. That is, it is the amount of energy (erg) put out each second (s) in a wavelength range (Angstrom) which is radiated by a surface area (cm2) into a solid angle of space (steradian).

How long is a Planck unit? ›

Planck length

It is equal to 1.616255(18)×1035 m (the two digits enclosed by parentheses are the estimated standard error associated with the reported numerical value) or about 1020 times the diameter of a proton.

What is the dimension of Planck constant? ›

∴ The dimensional formula of Planck's constant h is [ML2T-1]. It is the rotational equivalent of linear momentum. Where, L = angular momentum, I = moment of inertia, ω = angular momentum, r = distance and p = linear momentum.

What is the symbol for Planck's law? ›

Planck further assumed that when an oscillator changes from a state of energy E1 to a state of lower energy E2, the discrete amount of energy E1 − E2, or quantum of radiation, is equal to the product of the frequency of the radiation, symbolized by the Greek letter ν and a constant h, now called Planck's constant, that ...

What is the value of Planck's energy? ›

Planck's constant is a physical constant which is denoted by 'h'. It was given by Max planck. It value is 6.626×10−34 Js.

What has the same unit as Planck's constant? ›

The unit of planck's constant is equivalent to that of angular momentum. Their dimensional formulas are the same but both physical quantities are not the same. Planck's constant gives the relation between energy and frequency. The formula which expresses this relation is $E = h\nu $.

What are the units of the Planck constant? ›

The Planck constant has the same dimensions as action and as angular momentum. In SI units, the Planck constant is expressed with the unit joule per hertz (J⋅Hz1) or joule-second (J⋅s).

How is Planck's constant measured? ›

The accepted value of the Planck constant, 6.626 070 15 × 1034 J s, is obtained from one of the most precise methods, the Kibble balance, which involves the quantum Hall effect, the Josephson effect, and the use of the international prototype of the kilogram or its copies.

What is Planck's equation used for? ›

Planck's law helps us calculate the energy of photons when their frequency is known. If the wavelength is known, you can calculate the energy using the wave equation to calculate the frequency and then apply Planck's equation to find the energy.

What is the H cut symbol? ›

Ħ (minuscule: ħ) is a letter of the Latin alphabet, derived from H with the addition of a bar. It is used in Maltese for a voiceless pharyngeal fricative consonant (corresponding to the letter heth of Semitic abjads: Arabic: ح, Hebrew: ח). Lowercase ħ is used in the International Phonetic Alphabet for the same sound.

What is the value of c in physics? ›

The speed of light c = 299792458 m/s ≅ 3 × 108 m/s. The velocity of light can be expressed in terms of mph or km/s. That is- The speed of light in mph 186,000 miles per hour. The speed of light in air is 299792 km/s.

What is Planck's constant in eV? ›

Physics Today, August 1997
Planck constanth6.6260755E-34
Planck constant in eVh4.1356692E-15
Planck constant over 2phbar1.05457266E-34
Planck constant over 2p in eVhbar6.5821220E-16
96 more rows

What is k in physics? ›

Generally, as others have stated, K usually mean Kelvins, and can also stand for kinetic energy (especially if paired with U and E, which typically represent potential energy and total energy, respectively). The lower case k is a little more broad. In heat transfer it usually means the conduction coefficient.

Top Articles
Latest Posts
Article information

Author: Dan Stracke

Last Updated:

Views: 6191

Rating: 4.2 / 5 (63 voted)

Reviews: 94% of readers found this page helpful

Author information

Name: Dan Stracke

Birthday: 1992-08-25

Address: 2253 Brown Springs, East Alla, OH 38634-0309

Phone: +398735162064

Job: Investor Government Associate

Hobby: Shopping, LARPing, Scrapbooking, Surfing, Slacklining, Dance, Glassblowing

Introduction: My name is Dan Stracke, I am a homely, gleaming, glamorous, inquisitive, homely, gorgeous, light person who loves writing and wants to share my knowledge and understanding with you.