Paradox of radiation of charged particles in a gravitational field electric field has an accompanying magnetic field, and the whole oscillating electromagnetic radiation field propagates independently of the accelerated charge, carrying away momentum and energy. The energy in the radiation is provided by the work that accelerates the charge. The theory of general relativity is built on the equivalence principle of gravitation and inertia. This principle states that it is impossible to distinguish through any local measurement whether one is in a gravitational field or being accelerated. An elevator out in deep space, far from any planet, could mimic a gravitational field to its occupants if it could be accelerated
Refraction of incidence "θ" and angle of refraction "θ" is equal to the ratio of phase velocities ("v" / "v") in the two media, or equivalently, to the indices of refraction ("n" / "n") of the two media. Optical prisms and lenses utilize refraction to redirect light, as does the human eye. The refractive index of materials varies with the wavelength of light, and thus the angle of the refraction also varies correspondingly. This is called dispersion and causes prisms and rainbows to divide white light into its constituent spectral colors. Consider a wave going from one material to another where