The resolution of a telescope where objective has a diameter of 200 inches when the light of wavelength 4000 Å is coming from the star is

$9.606\times 10^{-8} rad$

The correct answer is option (1) : $9.606\times 10^{-8} rad$

 The limit of resolution $Δθ$ is given by

$Δθ≈\frac{0.61\lambda }{a}, \lambda = 4000\times 10^{-10}m$ and $a=100$ inches

$⇒\lambda = 4000 \times 10^{-10}$ and $a=100\times 0.0254=2.54\, m$

$Δθ ≈\frac{0.61\times 4 \times 10^{-7}}{2.54}=0.9606\times 10^{-7}$

$≈9.606\times 10^{-8} rad$