Two astronauts performing a spacewalk are 20 m apart
PHYSICS · Single correct · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics
Problem
Two astronauts performing a spacewalk are 20 m apart, surrounded by nearly perfect vacuum. Astronaut A strikes a metal bar against the handrail to produce a loud clang and simultaneously flashes a strobe light toward astronaut B. Astronaut B sees the flash but hears no sound. Which of the following statements BEST explains this observation?
(a) The clang's frequency is ultrasonic, so sound cannot be detected, whereas light of any frequency travels in vacuum.
(b) Sound intensity decreases rapidly in the near-vacuum between the astronauts, becoming too faint to hear, while light intensity is essentially unchanged.
(c) Sound requires a material medium to propagate, whereas light does not; in the vacuum only the light reaches astronaut B.
(d) Light travels so much faster than sound that, over the 20m separation, the flash arrives immediately while the sound will be heard much later, giving the impression it is absent.