In double slit experiment, the angular width of the fringes is `0.20^@` for the sodium light `(lambda=5890Å)`. In order to increase the angular width of the fringes by `10%`, the necessary change in the wavelength is
A. (a) Increase of `589Å`
B. (b) Decrease of `589Å`
C. (c) Increase of `6479Å`
D. (d) Zero