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 $6400\stackrel{\circ }{A}$ 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)

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

Limit of resolution $=\theta =\frac{1.22\times \text{wavelength of light}}{\text{diameter of objective}}=\frac{1.22\lambda }{d}=\frac{1.22\times 6400\times {10}^{-10}}{200\times {10}^{-12}}=39\times {10}^{-8}rad$