Two charged bees land simultaneously on flowers that are separated by a finite distance. for a few moments, the charged bees rest on the flowers. the charged bees both generate an electric field, and while the charged bees are resting on the flowers, the net electric field at some distance between them is zero. (a) do the bees have the same or opposite signs of charge?
same, the electric fields point in opposite directions and therefore cancel at some midpoint.
same, the electric fields multiply together to equal zero.
opposite, the electric fields point in the same direction summing to zero.
opposite, the net electric field due to the two bees points in a direction perpendicular to the direction from one bee to the other.

Same, the electric fields point in opposite directions and therefore cancel at some midpoint.

Explanation:

The Electric field net at some point between them is zero, only if they point in opposite direction (they cancel to the each other). In order the electric fields  have opposite direction, at some point between the bees , the bees must have the same sign of electric charge

positive reinforcement? ?

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.