( I initially started to ask, "since according to Quantum-theory of light; the energy of a photon, depends only on the frequency of light-wave (E = h * nu), and no-mention of amplitude. So, does the energy of light doesn't depend upon amplitude?" But that question has already asked by >1 users , but I have 1 more question related to that )
Some of the other-answers suggests, the EMWs having same frequency but different amplitude, is a mixture-condition of photons.
Then, is-it really impossible to synthesize an electromagnetic wave of such an amplitude, so-that the energy is NOT an integral multiple of the basic photon's energy, using a dipole antenna and an oscillator ? like this? Fig-1, Electromagnetic-waves could be synthesized by creating an oscillating electric field in a dipole antenna. (image from http://www.kshitij-iitjee.com/production-of-electromagnetic-waves-by-an-antenna)
I think, in this-way, all-kinds of frequencies and amplitudes could be synthesized (at-least theoretically). Fig 2. EMWs with same frequency but varying amplitude. in Wave-2, I choose the value randomly, just to say, any-value could be placed arbitrarily. Neglect drawing-errors.
Then , what-thing restricting the antenna-system to produce an wave with such an amplitude?
Related question : Where is the amplitude of electromagnetic waves in the equation of energy of e/m waves? Where is the amplitude of electromagnetic waves in the equation of energy of e/m waves?