A) \[10,5,\frac{5}{2}\]
B) \[20,\frac{20}{3},\frac{20}{5}.....\]
C) \[30,20,10.....\]
D) \[35,25,15.....\]
Correct Answer: B
Solution :
Path difference \[\Delta x(SA+AP)-SP\] \[\Rightarrow \] \[\Delta x=(65+65)-120\] \[\Rightarrow \] \[\Delta x=10\,m\] But at A the wave suffers reflection at the surface of rigid/fixed end or denser medium hence the wave must suffer an additional path change of \[\frac{\lambda }{2}\]on a phase change of\[\pi \]. \[\Rightarrow \]Net path difference \[=\left( 10-\frac{\lambda }{2} \right)\] For maxima (constrictive interference) Net path difference \[=(2n)\frac{\lambda }{2},n=0,1,2,3....\] \[10-\frac{\lambda }{2}=(2n)\frac{\lambda }{2};n=0,1,2,....\] \[\Rightarrow \] \[10=(2n+1)\frac{\lambda }{2};n=0,1,2,.....\] \[\Rightarrow \] \[\lambda =\frac{20}{2n+1};n=0,1,2,....\] \[\Rightarrow \] \[\lambda =20,\frac{20}{3},\frac{20}{5},\frac{20}{7}.....\]You need to login to perform this action.
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