The formula you provided, E=mc^2, is indeed the energy-mass equivalence formula from Albert Einstein's theory of special relativity. However, it's important to clarify that this formula applies to objects with mass, not to photons.
For particles with mass (like your 1-kilogram object), you can use this formula to calculate their energy when they are at rest (their rest energy) or when they are moving at a constant velocity (their kinetic energy).
However, photons are massless particles. According to the theory of special relativity, particles with zero rest mass, like photons, travel at the speed of light in a vacuum (c), and their energy is not given by the same formula.
The correct formula for calculating the energy of a photon is given by the Planck-Einstein relation:
E = hf
where E is the energy of the photon, h is the Planck constant (approximately 6.626 x 10^-34 joule-seconds), and f is the frequency of the photon.
Alternatively, you can use the formula in terms of the photon's wavelength (λ):
E = hc / λ
where λ is the wavelength of the photon, and c is the speed of light in a vacuum (approximately 299,792,458 meters per second).
It's important to recognize that the energy of a photon is solely determined by its frequency (or equivalently, its wavelength) and is not related to mass or velocity in the way that the energy of a massive object is calculated. The energy of a photon is purely quantized in terms of its electromagnetic properties.