A) 98 cm
B) 100 cm
C) 150 cm
D) 200 cm
Correct Answer: A
Solution :
In Galilean telescope a convergent lens is used as the objective and a divergent lens as the eye piece. Magnifying power and length of telescope are written as: \[M=\frac{{{f}_{o}}}{{{u}_{e}}}\] and \[L={{f}_{o}}-{{u}_{e}}\] In normal adjustment, i.e., in relaxed eye state \[{{u}_{e}}={{f}_{e}}\] So,\[{{M}_{\infty }}=\frac{{{f}_{o}}}{{{f}_{e}}}=50\]or \[{{f}_{e}}=\frac{{{f}_{o}}}{50}=\frac{100}{50}=2\,cm\] and \[{{L}_{\infty }}={{f}_{o}}-{{f}_{e}}\] \[\therefore \] \[{{L}_{\infty }}=100-2=98\,cm\]
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