# Formula: Photoelectric Effect Energy    Cutoff wavelength

## Work Function

Unit
Work function is the energy that must be expended to knock an electron out of a solid (e.g. out of a metal plate). Usually, the work function is given in the unit "eV" (electron volt): $$1 \, \mathrm{eV} = 1.6 \cdot 10^{-19} \, \mathrm{J}$$

## Cutoff wavelength

Unit
Cutoff wavelength is the minimum wavelength that light must have in order to be able to knock electrons out of a metal plate.

## Planck's Constant

Unit
Planck's constant $$h$$ is a physical constant from quantum mechanics and has the following exact value: $$h ~=~ 6.626 \, 070 \, 15 ~\cdot~ 10^{-34} \, \mathrm{Js}$$

## Speed of light

Unit
Speed of light is a physical constant and indicates how fast light travels in empty space (vacuum). It has the following exact value in vacuum: $$c ~=~ 299 \, 792 \, 458 \, \frac{ \mathrm{m} }{ \mathrm{s} }$$

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