A) infinite
B) 6 m
C) 4m
D) 3m
Correct Answer: B
Solution :
Let\[S\]be the light source. If light falls on the surface at critical angle\[C\], it grazes along the surface as shown. \[\sin C=\frac{1}{n}=\frac{3}{5}\] From\[\Delta QSR\], we have \[\tan C=\frac{QR}{QS}=\frac{r}{4}\] \[\Rightarrow \] \[\frac{3}{4}=\frac{r}{4}\] \[\Rightarrow \] \[r=3\] Hence, diameter\[=2r=2\times 3=6\,\,m\]You need to login to perform this action.
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