$$ Thermal mass transfer.
I know they say a photon **doesn't** have a [REST] mass.
Tom Roberts wrote: -=-SNiP-=- -=- eV/c^2. -=-

$$ The GUESS iSS test REST mass is, eM/c^2.

In SR [& GR], they have changed the meaning of the word, 'mass.'

$$ Conspiring with SOME economically-associated collaborates, etc.

[The GR] Mass no longer means mass, as it is used in all other
sciences. In SR [and also GR], they today only allow the word
'mass' to mean 'rest mass.' Those in SR [and GR] are too weak
to use mass the way everyone [General Science] else uses this
word [mass].
-=-
So a photon, never being at rest, still has to have mass, as
it [GENERAL mass] is defined in all other [SI General] sciences.
-=-
Therefore, a photon is a real particle of [GENERAL SI] mass, as
[General Scientists and many many (Non-GR)] others would say it.

wrote:
But do we know the amount of energy a single photon can
produce [as ABSORBED by a detector] and then use E=mc^2
thus [the EQUiVALENT mass] m = E/c^2 [as ABSORBED mass.] -=-

$$ THERMAL mass transfer (radiation light).
$$ A photon EMiTTED with energy h*f, subs ..h*f/c^2, mass.
$$ A photon ABSORBED with energy h*f adds ..h*f/c^2, mass.

$$ Think of this as you would MARBLEs in your GARDEN HOSE.
$$ [ONE's Loss Marble is ANOTHER's gain ..and visa-versa].
$$ Newton's Cradle ..a desktop MODEL of Light Propagation.

$$ Fridge Magnet = Suction Cup equation.
$$ Think of a Regrigerator Magnet as a Fridge Suction Cup.
$$ Each must do WORK in OVERcoming friction, or FALL down.
$$ Refrigerator Magnet = Fridge Suction Cups of Trembling.

$$ Hope this helps, ```Brian A M Stuckless, Ph.T (Tivity).

Tom [He between his error-bars] Roberts wrote: -=-
E single photon has energy E=hv, where h is Planck's constant,
and v is the frequency [as MEASURED] of the [says Tom] source.

is there a "theoretical" mass for a photon ???
Newton's Cradle THERMAL mass transfer analogy. End of POST.