Question

The diameter of the objective lens of a telescope is $250\text{cm}.$ For light of wavelength $600\text{nm}.$ Coming from a distant object, the limit of resolution of the telescope is close to-

• A. $1.5\times {10}^{-7}\text{rad}$
• B. $2.9\times {10}^{-7}\text{rad}$
• C. $4.5\times {10}^{-7}\text{rad}$
• D. $2.7\times {10}^{-7}\text{rad}$

Answer 1

The correct option is B $2.9\times {10}^{-7}\text{rad}$

Limit of resolution, $\theta =\frac{1.22\lambda }{d}$

$\theta =\frac{1.22\times 600\times {10}^{-9}}{250\times {10}^{-2}}\approx 3.0\times {10}^{-7}\text{rad}$
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Hence, $\left(C\right)$ is the correct answer.