"Comparing Formulas: E=p^2/2m and E=hf

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    E=hf Formulas
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The formulas E=p^2/2m and E=hf represent different concepts in physics. E=p^2/2m describes the kinetic energy of a classical particle, while E=hf refers to the energy of a quantum photon. The context is crucial for understanding these equations, as they apply to different scenarios in classical and quantum mechanics. The first formula is relevant for non-relativistic particles, whereas the second is specific to non-interacting photons. Understanding these distinctions is essential for grasping the principles of energy in both classical and quantum physics.
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What is the difference between formulas E=p^2/2m and E= hf ?
 
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You cannot understand a formula without its context. The first E in reality means: Energy of a non-relativistic, non-interacting, classical particle. The second E refers to the energy of a non-interacting, quantum photon.
 
p^2/2m is non-relativistic kinetic energy
E=hf usually means total energy of a photon
 

Thread 'Two equivalent statements of time reversal symmetric Hamiltonian'

Time reversal invariant Hamiltonians must satisfy ##[H,\Theta]=0## where ##\Theta## is time reversal operator. However, in some texts (for example see Many-body Quantum Theory in Condensed Matter Physics an introduction, HENRIK BRUUS and KARSTEN FLENSBERG, Corrected version: 14 January 2016, section 7.1.4) the time reversal invariant condition is introduced as ##H=H^*##. How these two conditions are identical?
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