r = distance of moon from earth = 3.84 x 10⁸ m
R = size of the object on moon = 0.67 m
D = diameter of the lens = ?
[tex] \lambda [/tex] = wavelength of light = 550 x 10⁻⁹ m
Using the equation for Rayleigh criterion
R/r = 1.22 [tex] \lambda [/tex]/D
inserting the values
0.67/(3.84 x 10⁸) = 1.22 (550 x 10⁻⁹) /D
D = 384.6 m