Student Q&A (click to open)
Q1. What exactly is “refraction” in this simulation?
In the top view, the puck is a “light corpuscle”. It moves in a straight line until it reaches a boundary.
After that, its direction changes — that’s refraction.
The dashed line is the normal. Angles θ are measured from that normal.
Q2. What stays the same at the boundary?
In Newton’s explanation, the boundary force acts normal to the surface. So there is (approximately) no sideways force.
That means the parallel component stays the same:
v∥ (before) = v∥ (after)
Q3. What changes at the boundary, and why does the ray bend?
The normal component increases because Newton imagined the denser medium attracts the corpuscles near the surface.
So:
v⊥ increases while v∥ stays the same
If the “downward” component gets bigger but the sideways component doesn’t, the velocity points more toward the normal.
Q4. Why does “Realism mode” have a thin interaction zone?
Because Newton’s force was meant to be short-range, acting mainly as the corpuscle crosses the interface.
In realism mode, the attraction only acts when the puck is close to the boundary (within the zone width slider).
That’s the “mid-ramp” phase you mentioned.
Q5. Is Newton’s explanation correct?
It explains Snell’s law neatly using components — but it predicts that light travels faster in denser media.
Later measurements found light travels slower in denser media, supporting wave ideas and later EM theory.
So Newton’s mechanism is historically important, but physically wrong on the speed prediction.
Q6. What should I do to test understanding?
Try these:
• Increase the boost: does θ₂ move closer to the normal?
• Rotate φ: how do θ₁ and θ₂ change?
• Turn on realism + friction: does the “perfect conservation” become messy?
• Switch off v∥/v⊥: can you still explain the bend just from vectors?