In a Young’s double–slit arrangement, monochromatic light of wavelength 600 nm falls normally on two parallel slits that are 0.40 mm apart. The interference pattern is observed on a screen 2.0 m away from the slits.
(a) Write the expression for the fringe width and calculate its value for the given data.
(b) If the slit separation is doubled while all other experimental conditions remain unchanged, qualitatively explain how the interference pattern will be affected with respect to (i) fringe width and (ii) number of fringes visible in the central portion of the screen.
(c) Without performing fresh calculations, state the new numerical value of the fringe width and give a brief reason for your answer.