MCQ
A sound wave of wavelength $32 cm$ enters the tube at $S$ as shown in the figure. Then the smallest radius $r$ so that a minimum of sound is heard at detector $D$ is ... $cm$
- A$7$
- ✓$14$
- C$21$
- D$28 $
✓
Answer
Correct option: B.
$14$
b
(b) Path difference $(\pi r - 2r) = \frac{\lambda }{2} = \frac{{32}}{2} = 16$,
(b) Path difference $(\pi r - 2r) = \frac{\lambda }{2} = \frac{{32}}{2} = 16$,
$r = \frac{{16}}{{\pi - 2}} = 14\,cm$.
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