Photon Momentum (p = h/λ)

p = \frac{h}{\lambda}

p =

λ =

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Constant used — built into this formula, no need to enter

h = 6.62607015 \times 10^{-34}\ \text{J}{\cdot}\text{s}

Planck constant · exact

Learning zone

Light pushes. Each photon delivers p = h/λ of momentum when absorbed, twice that when reflected — tiny per photon, but sunlight exerts about 9 μN on every square meter of a perfect mirror at Earth's distance. Add up enough area and it becomes propulsion: solar sails like IKAROS and LightSail 2 have flown on nothing else, and comet tails point away from the Sun partly for the same reason.

Photon Momentum (p = h/λ)

p = \frac{h}{\lambda}

Where

$p$ = Photon momentum
$\lambda$ = Wavelength

Missing one of these? Work it out first, then come back

Photon momentum — Linear Momentum (p = mv), Impulse (J = FΔt)
Wavelength — Photon Energy from Wavelength (E = hc/λ), Wave Speed (v = fλ)

Part of this formula set

Photon and quantum relations

7 formulasThe small family of relations built on Planck's constant — photon energy and momentum, matter waves, the photoelectric effect and the Bohr levels.