A beam of light of wavelength 600 nm from a distance source falls on a single slit 1 mm wide and resulting diffraction pattern is observed on a screen 2m away. What is the distance between the first bright fringes on either side of the central bright fringe ?

Explanation

In case of diffraction, apart from central maxima the position
of the first maxima is given by `( a sin theta=(3lambda)/2)`
`rArr sin theta = (3lambda)/(2a)`
From geometry of the figure `sin theta =y/D`
From Eqs (i) and(ii), we get
`y= (3 lambdaD)/(2a)=(3xx600xx10^(-9)mxx2m)/(2xx1xx10^(-3)m)=1.8mm`
:. The distance between the first maxima on either side
`=2y = 3.6mm`