A) 420 nm
B) 500 nm
C) 450 nm
D) 490 nm
Correct Answer: C
Solution :
For reflection at the air-soap solution interface, the phase difference is \[\pi \]. For reflection at the interface of soap solution to glass also, there will be a phase difference of\[\pi \]. \[\therefore \] The condition for the maximum intensity \[=2\mu t=n\lambda \] For n, \[n{{\lambda }_{1}}=(n-1){{\lambda }_{2}}\] \[n\times 420=(n-1)\,\,630\] \[\therefore \] \[n\,(630-420)=630\] \[\Rightarrow \] \[n\,(210)=630\] \[\Rightarrow \] \[n=\frac{630}{210}\] \[\Rightarrow \] \[n=3\] This is the maximum order, where they coincide \[2\times 1.4\times t=3\times 420\] \[\Rightarrow \] \[t=\frac{3\times 420}{2\times 1.40}=450\,\,nm\]You need to login to perform this action.
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