A hollow cylinder is lit by sunlight at \(45^\circ\) as shown on the left. If seen from a fixed point, which option is the closest representation of the lit area inside the cylinder?
Show Hint
For light-and-shadow problems:
\begin{itemize}
\item Light travels in straight lines,
\item Combine top and side views to infer the 3D illuminated region,
\item Curved surfaces produce smoothly varying light boundaries.
\end{itemize}
Step 1: Sunlight enters the hollow cylinder at an angle of \(45^\circ\). Hence, the illuminated region on the inner surface follows the direction of the incoming rays.
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Step 2: From the top view, the sunlight strikes only a portion of the inner circumference. From the side view, the rays form a slanted band across the height of the cylinder.
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Step 3: The visible lit area is therefore a \emph{continuous, slanted elliptical-like patch} on the inner curved surface, bounded by the circular opening and the angular direction of light.
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Step 4: Comparing the options:
\begin{itemize}
\item Options A, B, D: Show incorrect curvature or discontinuity inconsistent with straight-line light propagation.
\item C: Correctly represents the slanted, continuous illuminated region produced by light entering at \(45^\circ\).
\end{itemize}
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Final Answer:
\[
\boxed{C}
\]
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