The two slits are 1 mm apart from each other and illuminated with a light of wavelength `5xx10^(-7)` m. If the distance of the screen is 1 m from the slits, then the distance between third dark fringe and fifth bright fringe is

Options

A. 1.5 mm
B. 0.75 mm
C. 1.25 mm
D. 0.625 mm

Answer

C

Explanation

Distance of 5th bright fringe
`x_(5)= (5lambdaD)/(d)`
Distance of 3rd dark fringe
`x_(3)= ((2 xx 3-1)lambdaD)/(2d)= (5)/(2)(lambdaD)/(d)`
Required distance
`= x_(5)- x_(3)= (5)/(2)(lambdaD)/(d)= (5 xx 5 xx 10^(-7) xx 1)/(2 xx 10^(-3)) = 1.25 mm`