Question

Assume that the light of wavelength is $6000\mathring{A}$ coming from a star. What is the time resolution of a telescope whose objective has a diameter of $100$ inch?

• A. $3.66\times 10^{-7}$ rad
• B. $1.44\times 10^{-7}$ rad
• C. $2.9\times 10^{-7}$ rad
• D. $5.8\times 10^{-7}$ rad

Answer 1

Answer: (C)

Given, $\lambda =6000\mathring{A}$
$=6\times 10^{-7}m$
Diameter of objective lens, $a=100$ inch
$a=254cm$ $(\because$ 1 inch=254 cm)
$=2.54m$
Since, we know that
Resolution limit of a telescope
$d\theta =\frac{1.22\lambda }{a}$
$=\frac{1.22\times 6\times 10^{-7}}{2.54}$
$=2.88\times 10^{-7}$
$=2.9\times 10^{-7}$ rad