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AP4: Laser beams sent from the Earth reflect off retroreflectors left by Astronauts during the Appollo missions. The time it takes the light pulses to return allow us to determine the distance to the moon (which is getting almost 4cm farther away each year). These laser pulses (assume they are 532nm in wavelength) are sent through a telescope - until the 1980's this was done with a 2.7m diameter telescope at the Mcdonald Observatory. Treating the spread of the laser beam as being due to the diffraction of the light from the circular aperture, a) find the diameter of the beam when it reaches the moon (384,000 km away) b) repeat the calculation, but assuming the laser came from a laser pointer (3mm diameter)