In a Young's double slit experiment, the slit separation is `1mm` and the screen is `1m` from the slit. For a monochromatic light of wavelength `500nm`, the distance of 3rd minima from the central maxima is

Options

A. (a) `0.50mm`
B. (b) `1.25mm`
C. (c) `1.50mm`
D. (d) `1.75mm`

Answer

B

Explanation

Distance of `n^(th)` minima from central bright firnge
`x_n=((2n-1)lambdaD)/(2d)`
For `n=3` i.e. `3^(rd)` minima
`x_3=((2xx3-1)xx500xx10^-9xx1)/(2xx1xx10^-3)`
`=(5xx500xx10^-6)/(2)=1.25xx10^-3m=1.25mm`