If the distance b/w the first maxima and the fifthminima of a double slit patternis 7mm ano the slits are separated by 0.15mm with the screen 50cm from theslits,then wavelength of the light used is

a.600nm

b.525nm

c.467nm

d.420nm

let d be distance between slits

     X be distance between screen and slits

     L be yhe wavelength

    Distance of fifth minima from centre of screen = 9LX/(2d)

    distance of 1st maxima from centre of screen  = LX/d

  =>distance between 1st maxima and fifth minima = 7LX/(2d)

    =>  7LX/(2d) = 7mm

   substituting values of x and d , we get L = 600 nm  

ANS a.600nm

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