Question

A telescope using light having wavelength $5000A^o$ and using lenses of focal $2.5$ and $30cm$. If the diameter of the aperture of the objective is $10cm$, then the resolving limit and magnifying power of the telescope is respectively

• A. $6.1\times {10}^{-6}radand12$
• B. $5.1\times {10}^{-6}radand12$
• C. $6.1\times {10}^{-6}radand8.3\times {10}^{-2}$
• D. $5.1\times {10}^{-6}radand8.3\times {10}^{-2}$

Answer 1

Answer: (A)

$6.1\times {10}^{-6}radand12$

$m=\frac{f_0}{f_e}=\frac{30}{2.5}=12$
Resolving limit $=\frac{1.22\lambda }{a}=\frac{1.22\times (5000\times {10}^{-10})}{0.1}$
$=6.1\times {10}^{-6}rad$