Q: Assume that light of wavelength 6000 Å is coming from a star. What is the limit of resolution of a telescope whose objective has a diameter of 100 inch?

Sol: objective has a diameter of 100 inch ,

a = 100 inch = 254 cm , λ ≈ 6000 A° = 6 × 10^{-5} cm

∆θ = 1.22λ/a ≈ 2.9 × 10^{-7} radians