The star Sirius is actually a binary star $($i$.$e$.$ two stars very close to each other$).$ They are so close that they cannot be resolved into two stars with the naked eye. In order to be able to see them as two stars $($i$.$e$.$ to resolve them$)$ we need a telescope with a large size lens. Calculate the minimum diameter of the telescope objective lens that is needed. The angle that the two stars subtend on the Earth is $10$ arc$-$seconds. Take wavelength of light $=600$ nm$.$Conversion factors:$60$ arc$-$seconds $=1$ arc minute$\mathrm{.}60$ arc$-$minutes $=$ one arc degree$\mathrm{.}57\mathrm{.}296$ arc$-$degrees $=$ One radian.Answer: