In Young's double-slit experiment, the wavelength of light is changed from 7000A˚ to 3500A˚ while the separation between the slits is doubled. Which of the following is not true?
(1) The width of fringes changes.
(2) The colour of bright fringes changes.
(3) The separation between successive bright fringes changes.
(4) The separation between successive dark fringes remains unchanged.