On the earth surface g = GM/R^2 And at the hieight h g" = GM/ [R+h] ^2 g" = R^2/ [ R+h]^2 * g g" = {R/ [ R+h] }^2 * g g" = {6378/ 7083}^2 * 9.81 = 7.95 m/s^2 -------------------------------------- T^2 = 4π^2 (R+h) /g" T^2 = 4π^2 *7083 /7.95 T = 187.54s = 0.052 hour. ======================== Part B v = 2*π *[R+h] / T v = 2*π *[7.083] / 187.54s v = 0.24 km /s
The point of contact the path difference is zero but one of the interfering ray is reflected so the effective path difference becomes λ/2 thus the condition of minimum intensity is created in the center.
