Question

Scientists use laser range- nding to measure the distance to the moon with great
accuracy. A brief laser pulse is red at the moon, then the time interval is measured
until the \echo" is seen by a telescope. A laser beam spreads out as it travels because
it di racts through a circular exit as it leaves the laser. In order for the relected light
to be bright enough to detect, the laser spot on the moon must be no more than 1.0
km in diameter. Staying within this diameter is accomplished by using a special large-
diameter laser. If = 532 nm, what is the minimum diameter of the circular opening
from which the laser beam emerges? The earth-moon distance is 384,000 km.

Answer 1

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