Question: A solid is hemispherical at the bottom and conical above. If the surface areas of two parts are equal, then the ratio of radius and height of its conical part is
Options:
A) $ 1:3 $
B) $ 1:1 $
C) $ \sqrt{3}:1 $
D) $ 1:\sqrt{3} $
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Answer:
Correct Answer: C
Solution:
- Surface area of cone
= Surface area of hemisphere
$ \pi rl=2\pi l^{2} $
$ \Rightarrow $ $ l=2r $
Height of cone $ =\sqrt{l^{2}-r^{2}} $
$ =\sqrt{4r^{2}-r^{2}}=\sqrt{3}r $
Height of hemisphere $ =r $
$ \therefore $ Ratio $ =\frac{\sqrt{3}r}{r}=\frac{\sqrt{3}}{1}=\sqrt{3}:1 $