Question

Diameter of the objective lens of a telescope is $250cm$. For light of wavelength $600nm$, coming from a distant object, the limit of resolution of the telescope is close to?

• A. $2.0\times {10}^{-7}rad$
• B. $4.5\times {10}^{-7}rad$
• C. $3.0\times {10}^{-7}rad$
• D. $1.5\times {10}^{-7}rad$

Answer 1

The correct option is C $3.0\times {10}^{-7}rad$

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

Given: $\lambda =600nm$ or $600\times {10}^{-9}m$
$D=250cm$ or $250\times {10}^{-2}m$

Using given data limit of resolution of telescope can be found out as
$\theta =\frac{1.22\times 600\times {10}^{-9}m}{250\times {10}^{-2}m}$

$=2.928\times {10}^{-7}radian$

$\approx 3\times {10}^{-7}rad$

Final answer: (c)