In which direction does the electric field point at a position directly west of a negative charge?
A. North
B. West
O C. East
O D. South

East

Explanation:

Electric fields point in the direction of decreasing potential. If there is only one negative charge, the most negative spot would be directly where the charge is. If we measure the electric field to its west, the field would be pointing to the charge, which is to that point's east.

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.