A thin flake of mica (n=1.58) is used to cover one slit of a double-slit arrangement.The central point on the screen is occupied by the 7th brigth fringe.If lamda = 550nm, what is the thickness of the mica?
path difference d=(n-1)*thickness
The Attempt at a Solution
first, the paths above the glass must be the same.So they are not in consideration.
let l be the thickness of the glass,t be the length travelled by light in mica,x in air
In the air:
compare 4 and 3,
i came out, t=xn.
Then i started to consider the difference of wavelength,
because the wavelength in mica is shorter than in air.
I tried to subtract the sum of the pulses in air and mica and set it equals to 7 lamda,
but what came out is peculiar,
let m , n be the number of pulses in mica and air respectively,f=frequency
i suppose it being m/n = t/nx ......so that they can be cancelled out......
Please help for this:((