In the laser range-finding experiments of Example 17.10, the laser beam fired toward the moon spreads out as it travels because it diffracts through a circular exit as it leaves the laser. In order for the reflected light to be bright enough to detect, the laser spot on the moon must be no more than \(1 \mathrm{~km}\) in diameter. Staying within this diameter is accomplished by using a special large-diameter laser. If \(\lambda=532 \mathrm{~nm}\), what is the minimum diameter of the circular opening from which the laser beam emerges? The earth-moon distance is \(384,000 \mathrm{~km}\).