27. The angular resolution of a 10 cm diameter telescope at a wavelength of 5000Å is of the order of ?

27. The angular resolution of a 10 cm diameter telescope at a wavelength of 5000Å is of the order of ?

\( (a)\; 10^6 \, \text{rad} \)  

\( (b)\; 10^{-2} \, \text{rad} \)  

\( (c)\; 10^{-4} \, \text{rad} \)  

\( (d)\; 10^{-6} \, \text{rad} \)  

Answer :  \( (d)\; 10^{-6} \, \text{rad} \)  

\( \text{Angular resolution} \)

\( d\theta_{\min} = \frac{\lambda}{a} \)

\( = \frac{5000 \, \text{Å}}{10 \, \text{cm}} \)

\( = 5 \times 10^{-6} \)