Question

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

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

Answer 1

Answer: (C)

Limit of resolution $= \frac{1.22\lambda}{d} $
$= \frac{1.22 \times600 \times 10^{-9}}{250 \times10^{-2} } $
$ = 2.9 \times10^{-7} \text{rad} $