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A 1.5 mW laser pointer is directed 2.5 m onto a wall where it forms a spot of area 1mm^2. Estimate the power of a lamp emitting spherical waves to replace the laser pointer which produces a similar power per unit area on the wall as the laser pointer.
A 660 Hz sound wave is emitted in all directions from a point source. At waht distance from the source does the amplitude ratio of successive wavefronts drop below 1.1001 ( assume the speed of sound to be 330m/s
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