A) \[\text{42}0\text{ nm}\]
B) \[~\text{5}00\text{ nm}\]
C) \[~\text{45}0\text{ nm}\]
D) \[\text{49}0\text{ nm}\]
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 \[2\times 1.4\times t=3\times 420\] \[\Rightarrow \] \[\text{t =}\frac{\text{3 }\!\!\times\!\!\text{ 420}}{\text{2 }\!\!\times\!\!\text{ 1}\text{.40}}\text{= 450 nm}\]You need to login to perform this action.
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