## University Physics with Modern Physics (14th Edition)

The diameter D of the telescope determines the resolution. The resolving power is $\theta_{r}=1.22\frac{\lambda}{D}$. We are told that the resolving powers are to be identical. $$\frac{\lambda_1}{D_1}=\frac{\lambda_2}{D_2}$$ $$D_2=D_1 \frac{\lambda_2}{\lambda_1}=(8000000m)\frac{550\times10^{-9}m 2}{2.0\times10^{-2}m }=220m$$