Final answer:
It takes approximately 2.5 seconds for a pulse of laser light to make a round trip from Earth to the Moon and back. This time frame includes both the trip to the Moon and the return trip. Lunar astronauts have used corner reflectors to measure the exact distance to the Moon with high precision, considering the speed of light and atmospheric effects. Hence, the correct answer is option C.
Step-by-step explanation:
The time it takes for a pulse of laser light to reach the Moon and bounce back to Earth is approximately 2.5 seconds (option C). This is based on the fact that light takes about 1.3 seconds to travel from Earth to the Moon which is a single trip. Since the question asks for the round trip time, we double that duration to account for both the journey to the Moon and back to Earth, resulting in approximately 2.6 seconds, which is closest to option C.
The delay experienced during the Apollo missions was indeed a result of this travel time. The astronauts were not slow to respond; rather, the communications signal (which travels at the speed of light) had to make this round trip which is why a delay of about 3 seconds was observed.