3) For a red laser beam of wavelength 1 = 650 nm and waist w, = 0.5 m, a) how large would the spot be on the surface of the moon? The average earth-moon distance is 385,000 km. (note: you can use our width expression or the divergence angle to calculate this) b) Laser ranging is used to determine how far away the moon is from the earth using time of flight. You basically bounce a laser pulse off the moon and see how long the trip takes, How long would it take light to travel from Earth to the moon and back? c) Let's assume that the "mirror" on the moon and the detector on earth both have an area of 1 m and use that to estimate the fraction of the beam power that makes it back to earth. Assume the mirror is perfect, neglect any atmospheric effects and you can treat the intensity as constant across the beam (I don't intend for you to do any Gaussian integrals). If the power during the pulse was 10W, what power would you detect back on earth