When a transparent film of refractive index 1.5 is kept over one of the openings of a double slit experiment apparatus, the interference pattern is shifted through six successive maxima, towards the side, where the film was placed. What is the thickness of the film if the wavelength of light used in 6000 Å?

Options

A. 4200 nm
B. 5200 nm
C. 7200 nm
D. 6200 nm

Answer

C

Explanation

Fringe shift`=(X)/(lamda)(n-1)t`
Fringe slit `=6X and lamda=6xx10^(-7)m`
`therefore 6X=(X)/(6xx10^(-7))(1.5-1)xxt`
`therefore 36xx10^(-7)=(1)/(2)`
`therefore t=72xx10^(-7)m=72xx10^(-7)xx10^(9)nm=7200nm`