Momentum of Electromagnetic Radiation (p = U/c)

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p = U/c

What each symbol means

SymbolWhat it stands for
UEnergy (J)
c3×10⁸ m/s
pMomentum (kg·m/s)

When to use this

Absorption: p=U/c. Reflection: p=2U/c. Radiation pressure = I/c (absorb) or 2I/c (reflect). Solar sails.