is E=mc^2 related to light as wave motion or stream of particles or both
E=mc^2 is a formula derived by Albert Einstein that relates energy (E) to mass (m) and the speed of light (c). It is not specifically related to whether light behaves as a wave or a particle, but rather it is a general principle of energy-mass equivalence.
However, in the context of the wave-particle duality of light, the formula can be related to both wave and particle properties of light. The formula can be used to explain the particle-like behavior of light, as it shows that light has energy and can interact with matter as if it has mass. Additionally, the formula can also be used in the wave theory of light, as it shows the relationship between the energy of light and its frequency (which is related to its wave properties).
In summary, E=mc^2 is a fundamental principle of physics that can be applied to both wave and particle properties of light.