Q1.
Now, bend the pipe and try to see the candle flame again (Fig. 11.5b). Can you still see it?
Answer
No, the flame cannot be seen through the bent pipe — even though the flame is still burning at the same place and the pipe still points at it.
Straight pipe → flame visible
Bent pipe → flame not visible
Bent pipe → flame not visible
Why it happens: Light from the flame travels only in straight lines. In the straight pipe there is a clear straight path from the flame to your eye. When the pipe is bent, that straight path meets the wall of the pipe. The light strikes the inside wall and is stopped there, so nothing reaches your eye.
Tip: This is exactly why a periscope needs mirrors at its bends (Section 11.8.1). Light will not turn a corner by itself — it has to be turned by a mirror.