Question

# A. Lunar astronauts placed a reflector on the Moon’s surface, off which a laser beam is...

A. Lunar astronauts placed a reflector on the Moon’s surface, off which a laser beam is periodically reflected. The distance to the Moon is calculated from the round-trip time. To what accuracy in centimeters can the distance to the Moon be determined, if this time can be measured to 0.11 ns?

B. Lasers can be constructed that produce an extremely high intensity electromagnetic wave for a brief time—called pulsed lasers. They are used to ignite nuclear fusion, for example. Such a laser may produce an electromagnetic wave with a maximum electric field strength of 0.54×1011 V / m for a time of 0.9 ns. What is the energy in kJ delivered on a 0.91 mm2 area?

C. Conversations with astronauts on lunar walks had an echo that was used to estimate the distance to the Moon. The sound spoken by the person on Earth was transformed into a radio signal sent to the Moon, and transformed back into sound on a speaker inside the astronaut’s
space suit. This sound was picked up by the microphone in the space suit (intended for the astronaut’s voice) and sent back to Earth as a radio echo of sorts. If the round-trip time was 2.54 s, what was the approximate distance to the Moon in thousands of kilometers, neglecting any delays in the electronics?

D.Lasers can be constructed that produce an extremely high intensity electromagnetic wave for a brief time—called pulsed lasers. They are used to ignite nuclear fusion, for example. Such a laser may produce an electromagnetic wave with a maximum electric field strength of 2.46×1011 V / m for a time of 1.2 ns. What is the maximum magnetic field strength in the wave?

E. A radar used to detect the presence of aircraft receives a pulse that has reflected off an object 3.17×10−5 s after it was transmitted. What is the distance in kilometers from the radar station to the reflecting object?

#### Earn Coins

Coins can be redeemed for fabulous gifts.