Question

Assuming that light of wavelength $6000\mathring{\text{A}}$ is coming from a star. What is the limit of resolution of a telescope whose objective has diameter of $122\text{cm}?$

• A. $3\times {10}^{–7}\text{rad}$
• B. $6\times {10}^{–7}\text{rad}$
• C. $9\times {10}^{–7}\text{rad}$
• D. $7\times {10}^{–7}\text{rad}$

Answer 1

The correct option is B $6\times {10}^{–7}\text{rad}$

The limit of resolution of telescope in terms of wavelength $\lambda$ and objective diameter $D$ is given as,

$\Delta \theta =\frac{1.22\lambda }{D}=\frac{1.22\times 6000\times {10}^{-10}}{1.22}=6\times {10}^{-7}\text{rad}$