Some distant star is to be observed by some telescope of diameter of objective lens a, at an angular resolution of 3.0 × 10^-7 radian. If the…

Some distant star is to be observed by some telescope of diameter of objective lens $\displaystyle a$, at an angular resolution of $\displaystyle 3.0 \times 10^{-7}$ radian. If the wavelength of light from the star reaching the telescope is $\displaystyle 500$ nm , the minimum diameter of the objective lens of the telescope is $\displaystyle \_\_\_\_$ cm. (nearest interger)