Question

Calculate the limit of resolution of a telescope objective having a diameter of $200\text{cm}$, if it has to detect light of wavelength $500\text{nm}$ coming from a star.

• A. $610\times {10}^{-9}\text{radian}$
• B. $152.5\times {10}^{-9}\text{radian}$
• C. $457.5\times {10}^{-9}\text{radian}$
• D. $305\times {10}^{-9}\text{radian}$

Answer 1

The correct option is D $305\times {10}^{-9}\text{radian}$

The limit of resolution of a telescope is,

$\theta =\frac{1.22\lambda }{d}$

$=\frac{1.22\times 500\times {10}^{-9}}{2}$

$=305\times {10}^{-9}\text{rad}$

Hence, $\left(A\right)$ is the correct answer.