Question

With the help of a telescope that has an objective of diameter $200cm$, it is proved that light of wavelengths of the order of $6400\mathring{A}$ coming from a star can be easily resolved. Then the limit of resolution is

• A. $39\times {10}^{-8}deg$
• B. $39\times {10}^{-8}rad$
• C. $19.5\times {10}^{-8}rad$
• D. $19.5\times {10}^{-8}deg$

Answer 1

Answer: (B)

$39\times {10}^{-8}rad$

Given : $D=200cm=2m$ $\lambda =6400\times {10}^{-10}m=6.4\times {10}^{-7}m$
Limit of resolution of telescope $d\theta =\frac{1.22\lambda }{D}$
$⟹d\theta =\frac{1.22\times 6.4\times {10}^{-7}}{2}=39\times {10}^{-8}rad$