A) 10 cm
B) 20 cm
C) 40 cm
D) 15 cm
Correct Answer: B
Solution :
Focal length of convex lens \[\frac{1}{f}=(\mu -1)\left[ \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right]\] \[{{R}_{1}}=10\,cm,\]\[{{R}_{2}}=-10\,cm,\]\[\mu =1.5\] \[\frac{1}{f}=(1.5-1)\left[ \frac{1}{10}-\frac{1}{-10} \right]\] \[=0.5\left( \frac{2}{10} \right)\] \[f=\frac{10}{2\times 0.5}\] \[f=10\,cm\] Focal length of concave mirror = 10 cm \[\therefore \]Radius of curvature\[=2\times 10=20\,cm\]
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