Question

If the source of light used in a Young's double slit experiment is changed from red to violet,
(a) the fringes will become brighter
(b) consecutive fringes will come closer
(c) the intensity of minima will increase
(d) the central bright fringe will become a dark fringe

Answer 1

(b) consecutive fringes will come closer

Fringe width, $\beta =\lambda D/d$.
Wavelength of red light is greater than wavelength of violet light; so, the fringe width will reduce.