photon kinetic energy

nuby

How is a photon's energy determine in relation to it's wavelength and frequency?
For example, 20hz vs. 400ghz electromagnetic waves.

pmb_phy

The energy of a photon, E (which can be considered as all kinetic energy since the proper energy = E₀ = 0 and E = K + E₀ = K), is related to the photon's frequency, f, by E = hf where h = Planck's constant = 6.626068 × 10^-34m²kg/s.

Pete

nuby

can E=1/2mv^2 be applied to photons ever?
or E=mc^2

lbrits

The proper relativistic equation is
:[tex]E^2 = p^2c^2 + m^2 c^4[/tex], which works just fine for photons when [tex]m = 0[/tex].

For ordinary particles, one can Taylor expand [tex]E = \sqrt{p^2c^2 + m^2 c^4}[/tex] to get a non-relativistic equation most people use... but for photons, you can't do this, and [tex]E = pc[/tex] simply.

According to de Broglie, [tex]p = h \nu[/tex], of course.

pmb_phy

No.

Pete