Electrical resistance is the opposition a conductor offers to the migration of electrons. It depends on what material the wire is made of as well as the dimensions of the wire. Resistance generally increases with increasing temperature. In some materials, called superconductors, resistance decreases to zero at critically low temperature. Sunshine is light, which is part of the electromagnetic spectrum, all of which is produced by accelerating electric charges.
All light is electromagnetic waves, the result of electromagnetic induction.
An echo is simply reflected sound. Because sound from a small source spreads out via the inverse square law, sound intensity per unit area decreases with distance to the reflecting surface, and when reflected continues to decrease with distance. So the echo you hear is much less loud than the original sound. A rainbow results from the refraction and internal reflection that occurs in raindrops illuminated by sunlight. When light enters a water drop it is refracted.