Aspaceship travels at a speed of 0.95c to the nearest star, alpha centauri, 4.3 light years (ly) away. how long does the trip take from the point of view of the passengers on the ship?

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