What is the effect on the interference fringes in a Young’s double-slit experiment due to each of the following operations:
(a) the screen is moved away from the plane of the slits,
(b) the (monochromatic) source is replaced by another (monochromatic) source of shorter wavelength,
(c) the separation between the two slits is increased
(d) the source slit is moved closer to the double-slit plane,
(e) the width of the source slit is increased
(f ) the monochromatic source is replaced by a source of white light? ( In each operation, take all parameters, other than the one specified, to remain unchanged.)

Explanation

Angular separation of the fringes remains constant `(lambda"/"d)`. The actual separation of the fringes increases in proportion to the distance of the screen from the plane of the two slits.