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If photons (light) is made of particles, which cannot be slowed down, but when in large numbers act as a wave (Which can be slowed down), how can we fully know that light cannot be slowed down. An example would be when you shine a light at a mirror. That light hits the mirrors surface, then the photons bounce off the surface of the mirror back in the other direction. But in order for them to do that, wouldn't they also have to stop to reverse direction. Even if only for a moment?


When light is "slowed" within a material, the particles do not actually slow down. They are temporarily absorbed into the atoms of the material. They are held for a very short time, and then emitted back into the world. These small delays are what make the light appear to move slower. With reflection, the effect is similar. The particles are absorbed into the material, and then emitted back. Due to interference effects, the strongest path is usually "angle in" equals "angle out".

Dr. Ken Mellendorf

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