A) 440 cm
B) 44 cm
C) 40 cm
D) 4 cm
Correct Answer: C
Solution :
Key Idea: Length of telescope and magnification will conclude the result. For an astronomical telescope, magnification \[M=\frac{{{f}_{o}}}{{{f}_{e}}}\] Length of telescope tube \[L={{f}_{o}}+{{f}_{e}}\] Given: \[M=10,\text{ }L-44\text{ }cm\] \[\therefore \] \[\frac{{{f}_{o}}}{{{f}_{e}}}=10\] and \[{{f}_{o}}+{{f}_{e}}=44\] \[\Rightarrow \] \[{{f}_{e}}=\frac{{{f}_{o}}}{10}\] So, \[{{f}_{o}}+\frac{{{f}_{o}}}{10}=44\] or \[\frac{11\,{{f}_{o}}}{10}=44\] or \[{{f}_{o}}=40cm\]
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