Physics · Optics
A highly collimated laser beam with a diameter of 1 cm and wavelength 500 nm is directed from the Earth's surface towards the Moon (approx. 384,000 km away). Assuming ideal diffraction-limited propagation in vacuum, which of the following best estimates the diameter of the beam upon returning to the Earth after reflection from an ideal flat reflector installed on the Moon?
Verified Solution4 OptionsUpdated: October 2026👁️1 View
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- 1200 km
- 220 km✓
- 320 m
- 4200 m
Correct answer
20 km
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