If vec A and vec B are vectors and vec B = -vec A , which of the following is true ? a) The magnitude of is equal to the negative of the vec B magnitude of vec A

b) Ā and vec B are perpendicular .

c) The direction angle of is equal to the direction angle of vec B A plus 180 degrees

d ) vec A + vec B =2 vec A .

With the simplified model of the eye, what corrective lens (specified by focal length as measured in air) would be needed to enable a person underwater to focus an infinitely distant object? (be careful-the focal length of a lens underwater is not the same as in air! assume that the corrective lens has a refractive index of 1.62 and that the lens is used in eyeglasses, not goggles, so there is water on both sides of the lens. assume that the eyeglasses are 1.90