(a) If the width of each slit is comparable to the wavelength of light used, the interference pattern thus obtained in the double-slit experiment is modified by diffraction from each of the two slits
(b) Given that: Wavelength of the light beam,
`lambda_(1)=590 nm=5.9xx10^(-7)m`
Wavelength of another light beam, `lambda-(2)=596nm=5.96xx10^(-7)m`
Distance the slits from the screen `=D=1.5m`
Distance between the two slits `alpha=2xx10^(-4)m`
For the first secondary maxima,
`sintheta=(3lambda_(1))/(2alpha)=(chi_(1))/(D)`
`chi_(1)=(3lambda_(1)D)/(2alpha) and chi_(2)=(3lambda_(2)D)/(2alpha)`
`therefore` Separation between the positions of first secondary maxima of two sodium lines
`chi_(1)-chi_(2)(3D)/(2alpha)(lambda_(2)-lambda_(1))`
`=(3xx1.5)/(2xx2xx10^(-4))(5.96xx10^(-7)-5.9xx10^(-7))`
`=6.75xx10^(-5)m`