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A soap film of thickness 0.0011 mm appea...

A soap film of thickness 0.0011 mm appears dark when seen by the reflected light of wavelength 580 nm.. What is the index of refraction of the soap solution, if it is known to be between 1-2 and 1.5 ?

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The correct Answer is:
A, B, C
Given `d=0.0011xx10^-3m`
for minimum reflection of light `2md=nl`
`rarr mu=(nlamda)/(2d)=(2nlamda)/(4d)`
`=(580x10^-9xx(2n))/(4xx11xx10)`
`=(58(2n))/44=0.132(2n)`
Given that `mu` has a value in between 1.2 and 1.5.
`rarr when n=5, `mu=0.132xx10=1.32`
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