What directions does light travel?

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Probably the simplest answer is that light travels in all directions. That does need some clarification, though, so let's start with how light is produced. Light is produced when a charged particle vibrates. That electrical vibration induces a magnetic one. Those paired vibrations then propagate outward from the source, as "a series of concentric spheres spaced in accordance with the vibration of the source." Imagine a pebble being dropped into a still pond. The waves move outward in concentric spheres. With that said, light will reach a destination; therefore, a line can be drawn, perpendicular to the wave fronts, that runs from the source to the destination. This in turn causes people to say that light travels in a straight line. Those lines are called rays. If you are only examining a hypothetical single ray, then it is not possible to say that light travels in all directions. Things can be complicated even more once you introduce refraction, reflection, and diffraction. A reflected light wave will change directions. The other two interactions will cause light to bend in a new direction.

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