A flake of glass (refractive index 1.5) is placed over one of the opening of a double-slit apparatus. The interference pattern displaced itself through seven successive maxima toward the side where the flake is placed. If wavelength of the light is `lambda = 600 nm`, then the thickness of the flake is

Options

A. 2100 nm
B. 4200 nm
C. 8400 nm
D. none of above

Answer

c

Explanation

(Shift) `= 7` (Position of central maxima)
`implies (mu - 1)t (D)/(d) = 7 ((lambda D)/(d))`
`:.t = (7 lambda)/(mu - 1)`
` implies t = (7(600))/(0.5)`
`implies t = 8400 nm`