When the actual location of a rock on a riverbed is different from where an observer on dry land sees it, the principle of is involved.
a) reflection
b) refraction
c) diffraction
d) total internal reflection

Large electric fields in cell membranes cause ions to move through the cell wall. the field strength in a typical membrane is 1.0 x 10 7 n/c. what is the magnitude of the force on a calcium ion with charge +e? what is its acceleration? is it possible for a particle with the same charge as as calcium to have a different acceleration if placed at this location? what would change the acceleration: mass of the particle? diameter of the particle?