(a) State the expression for the linear fringe width produced on the screen in Young’s double–slit experiment, clearly identifying each symbol.
(b) Keeping the wavelength of light constant, qualitatively explain how the fringe width will change in each of the following independent situations:
(i) The distance between the two slits is doubled while the screen position remains unchanged.
(ii) The screen is moved twice as far from the double–slit while the slit separation remains unchanged.
(c) A student claims that halving the wavelength will double the fringe width. Examine this claim and give a reasoned explanation without performing a numerical calculation.