A research station on the ocean floor is connected to a surface buoy directly above it by a 200 m long steel support cable. At t=0, the station simultaneously sends three signals toward the buoy:
• A blue laser pulse propagating vertically through seawater (index of refraction n=1.33).
• A mechanical pulse traveling up the steel cable at 5.0×103m/s.
• A radio pulse transmitted through the seawater toward the buoy.
The buoy is equipped with detectors for optical, mechanical, and radio signals. Which statement about the order and approximate arrival times of the signals at the buoy is most accurate?
(a) The laser pulse reaches the buoy first, about 0.9μs after emission; the mechanical pulse follows roughly 40ms later, and the severely slowed radio pulse arrives last, after about 0.15s.
(b) Because 0.04ms is shorter than a microsecond, the mechanical pulse is detected first, then—almost simultaneously—the laser and radio pulses arrive about 0.9μs after emission.
(c) The radio and laser pulses arrive almost simultaneously, each after roughly 0.9μs, while the mechanical pulse is detected about 40ms later.
(d) The laser and radio pulses arrive after about 0.9μs each, but using a 1.5×103m/s speed for sound, the mechanical pulse is delayed to about 0.13s.