In a Young's double-slit experiment , the slits are separated by `0.28` mm and screen is placed `1.4` m away . The distance between the central bright fringe and the fourth bright fringe is measured to be `1.2` cm . Determine the wavelength of light used in the experiment .

Explanation

Distance between the silits d=0.28 ,mm `=0.28 xx10^(-3)` m
Distance between the slits and the screen `,D=1.4 m`
Distance between the central fringe and the fouth (n=4) Ftinge ,
`u=1.2 cm =1.2 xx10^(-2) m`
In case of a sonstrctive interence , we have the relation for the the distance between the two fringes as :
` u=nlamda (D)/(d)`
where
n= order of fringes =4
`lamda `= wavelength of light used
`therefore lamda =(ud)/(nD)`
`=(1.2 xx10^(-2)xx0.28 xx10^(-3))/(4xx1.4)`
`=6xx10^(-7)`
=600 nm
Hence , the wavelength of the light is 600 nm .