A 1.0 m long horizontal glass tube is evacuated so that its interior pressure is negligible. At one end of the tube, a laser emits a brief light pulse at the same instant a miniature loudspeaker emits a 2 kHz tone. A detector at the opposite end is capable of registering either form of wave. Which of the following describes what the detector records?
(a) It detects the light pulse after approximately 3.3×10−9s and the sound pulse about 2.9×10−3s later.
(b) It detects the light pulse after approximately 3.3×10−9s but never detects the sound pulse.
(c) It detects both pulses simultaneously, because each wave travels at the speed of light in vacuum.
(d) It detects neither pulse, because both waves require a material medium to travel through the tube.