Although it has energy E they say that energy of a photon can be equal to his mass 'm'.
but
E= mc2
and if mass is =0 then
E =pc
and this is available in classical electromagnetic theory while "If the rest mass of the photon were non-zero, the theory of quantum electrodynamics
would be "in trouble""
But I guess not because ...if the limit is the speed of light then we can obtain lower speeds for at least three photons and then we can calculate the
mass of a photon.
Because the key is the third photon brought into equation.
I mean if the energy and momentum of a photon is
E=hω=hv=hc/λ p=hk
where the wave number k = |k| = 2π/λ ω = 2πν is the angular frequency, and ħ = h/2π
But I wonder what will happen if we change the angular frequency....
I guess then we will obtain a photon with mass called "Diamond of light" that will affect the gravitational field in the point(s) where the mass of
the photons has increased by range of the polarization states of the photon.
The photon also carries spin angular momentum that does not depend on its frequency.
"The magnitude of its spin is and the component measured along its direction of motion, its helicity, must be ±ħ. These two possible helicities,
called right-handed and left-handed, correspond to the two possible circular polarization states of the photon."
"A non-zero rest mass would introduce a small damping factor in the inverse square Coulomb law of electrostatic forces. That means the
electrostatic force would be weaker over very large distances."
If we will use the cathodic current in certain limits of range then guess what will happen....safe and secure.