| NOUN | quantity | Planck's constant, h | the constant of proportionality relating the energy of a photon to its frequency |
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| Meaning | The constant of proportionality relating the energy of a photon to its frequency; approximately 6.626 x 10^-34 joule-second . | |
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| Synonym | h | |
| Broader | factor of proportionality, constant of proportionality | The constant value of the ratio of two proportional quantities x and y |