Question

Calculate the limit of resolution of a telescope. Objective having a diameter of $200cm$, if it has to detect light of wavelength $500nm$ coming from a star?

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

Answer 1

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

We know that:
Limit of resolution of telescope $=\frac{1.22\lambda }{D}$

Given: $\lambda =500nm$ or $500\times {10}^{-9}m$
$D=200cm$ or $200\times {10}^{-2}m$

Using given data limit of resolution of telescope can be found out as
$\theta =\frac{1.22\times 500\times {10}^{-9}m}{200\times {10}^{-2}m}$

$=305\times {10}^{-9}radian$

Final answer: (a)