A distance of 1.0 × 10^−2 meter separates successive
crests of a periodic wave produced in a shallow
tank of water. If a crest passes a point in the tank
every 4.0 × 10^−1 second, what is the speed of this
wave?
(1) 2.5 × 10^−4 m/s (3) 2.5 × 10^−2 m/s
(2) 4.0 × 10^−3 m/s (4) 4.0 × 10^−1 m/s