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REFERENCEscipy

scipy Documentation

📖 INDEX

# constants-pi
# constants-c
# constants-h
# constants-g
# constants-electron-mass
# constants-metric
# optimize-root
# optimize-minimize
# optimize-curve-fit
# optimize-linprog
# sparse-csr-matrix
# sparse-csc-matrix
# sparse-coo-matrix
# csr-matrix-data
# csr-matrix-count-nonzero
# csr-matrix-eliminate-zeros
# csgraph-connected-components
# csgraph-dijkstra
# csgraph-floyd-warshall
# csgraph-bellman-ford
# csgraph-depth-first-order
# spatial-delaunay
# spatial-convexhull
# spatial-kdtree
# spatial-distance-euclidean
# spatial-distance-cosine
# io-savemat
# io-loadmat
# io-whosmat
# interpolate-interp1d
# interpolate-univariatespline
# interpolate-rbf
# stats-describe
# stats-ttest-ind
# stats-kstest
# stats-normaltest
# stats-norm
# signal-convolve
# signal-detrend
# signal-spectrogram
# signal-lfilter
# integrate-quad
# integrate-dblquad
# integrate-odeint
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constants.h

AI & DATA SCIENCE // constants-h

scipy.constants.h is the Planck constant, in joule-seconds, a fundamental constant relating a photon's energy to its frequency in quantum mechanics.

Syntax

from scipy import constants
constants.h

Deep Dive Course

The Planck constant appears throughout quantum mechanics, most famously in the relation connecting a photon's energy to its frequency, E equals h times f. Since 2019, like the speed of light, the Planck constant's value has been fixed by international definition, as part of redefining the kilogram in terms of fundamental constants rather than a physical reference object, making its value exact rather than an experimentally measured approximation with uncertainty.

1Understanding constants.h

The Planck constant appears throughout quantum mechanics, most famously in the relation connecting a photon's energy to its frequency, E equals h times f. Since 2019, like the speed of light, the Planck constant's value has been fixed by international definition, as part of redefining the kilogram in terms of fundamental constants rather than a physical reference object, making its value exact rather than an experimentally measured approximation with uncertainty.

💡

Use constants.h together with a frequency to compute photon energy directly instead of looking up and hardcoding the Planck constant's numeric value yourself.

editor.html
from scipy import constants

print(constants.h)
localhost:3000

2Practical Example

Here is a real-world application of constants.h showing how it is used in production SciPy code.

editor.html
from scipy import constants

frequency = 5e14  # visible light, roughly green
energy = constants.h * frequency
print(f"{energy:.3e} joules")
localhost:3000

3Best Practices

Follow these guidelines when working with constants.h:

1. Use constants.h directly in energy/frequency calculations rather than hardcoding its numeric value

2. Check whether you need h or the reduced Planck constant, h-bar, which scipy.constants also provides separately as hbar, since physics formulas use different conventions

3. Keep consistent SI units throughout a calculation involving h, since it's expressed specifically in joule-seconds

⚠️

Tip: Use constants.h together with a frequency to compute photon energy directly instead of looking up and hardcoding the Planck constant's numeric value yourself.

editor.html
from scipy import constants

print(constants.h)
localhost:3000

Examples

Example 01Basic Usage
from scipy import constants

print(constants.h)
Example 02Advanced Example
from scipy import constants

frequency = 5e14  # visible light, roughly green
energy = constants.h * frequency
print(f"{energy:.3e} joules")

Best Practices

  • Use constants.h directly in energy/frequency calculations rather than hardcoding its numeric value
  • Check whether you need h or the reduced Planck constant, h-bar, which scipy.constants also provides separately as hbar, since physics formulas use different conventions
  • Keep consistent SI units throughout a calculation involving h, since it's expressed specifically in joule-seconds

Interview Question

Why did the Planck constant become an exactly defined value in 2019, rather than remaining an experimentally measured one?▼

Hint: Think about what physical standard was redefined around that same time.

In 2019, the kilogram was redefined in terms of the Planck constant instead of a physical reference object, the international prototype kilogram, a single physical cylinder that could theoretically change mass over time due to contamination or wear. By fixing the Planck constant to an exact defined numeric value and defining the kilogram in terms of it, along with the already-fixed speed of light and a precise definition of the second, the kilogram became defined by a stable physical law rather than a single physical artifact, which also had the side effect of making the Planck constant itself an exact value rather than a measured approximation.

Exercises

MediumPractice using constants.h in a real scenario.
View Solution
from scipy import constants

print(constants.h)

Frequently Asked Questions

Why did the Planck constant become an exactly defined value in 2019, rather than remaining an experimentally measured one?▼

In 2019, the kilogram was redefined in terms of the Planck constant instead of a physical reference object, the international prototype kilogram, a single physical cylinder that could theoretically change mass over time due to contamination or wear. By fixing the Planck constant to an exact defined numeric value and defining the kilogram in terms of it, along with the already-fixed speed of light and a precise definition of the second, the kilogram became defined by a stable physical law rather than a single physical artifact, which also had the side effect of making the Planck constant itself an exact value rather than a measured approximation.

Related Functions

constants-cconstants-electron-massnp-exp