In Young's double slit experiment, ten slits separated by a distance of 1 mm are illuminated by a monochromatic light source of wavelength $5 × 10^{–7} m$. If the distance between slit and screen is 2 metre, then separation of bright lines in the interference pattern will be

1.0 mm

$β=\frac{λD}{d}=\frac{5×10^{-7}×2}{10^{-3}}=10^{-3}m$

= 1 mm.