A conceptual question about waves and particles?

[physicshelp32]

Okay so I know that when a wave moves from a medium to a different medium that it changes in the direction if the speed cahnges. So when a wave moves slower it moves towards the normal. However, I have a lab question that says, "A small particle will have to speed up, in the direction perpendicular to the surface, if it is to bend its path twords the normal." It says to explain why this is true for a particle but not a wave. So can anyone explain to me why? I've been wracking my head on it for a couple hours now. I can see why the particle may not act like a wave, because as the wave enters the medium the top part is slower the but the things behind it moves slower. So this causes a bend, but a prticle is so tiny that it can't possibly be too affected by this. However, I don't get why it needs to go faster to move towards the normal.

P.S. I'm not sure if this is the right forum, so if its wrong could an admin move it for me?

 

[jbsteele]

Thanks!A particle is a single entity, which means that its movement is determined by the forces acting on it. For a particle to move towards the normal, it needs to experience a force that will cause it to accelerate in the direction of the normal. This force is usually created by the difference in the speed of the wave in the two media, as the faster moving wave in the second medium pushes the particle towards the normal. Waves, however, are made up of many entities, so they can be bent or refracted without the need for any force to act on them.