In Young’s double slit experiment the
separation d between the slits is 2 mm, the
wavelength $\lambda of the light used is 5896 \mathop A\limits^0 and
distance D between the screen and slits is
100 cm. It is found that the angular width of
the fringes is 0.20
o
. To increase the fringe
angular width to 0.21
o
(with same \lambda $ and D)
the separation between the slits needs to be
changed to