In a diffraction experiment, a coherent light source illuminates a pair of identical slits in a barrier, and the resulting pattern is projected on a screen that is separated from the barrier by $2\mathrm{.}25$ m $.$ A student sketches the pattern that appears on the screen. The locations of the centers of the bright and dark fringes are accurate, but the shading is only qualitative. The color chosen may not be an ideal match to the actual light source.

Part $($a$)$

Enter the ratio of the slit separation, d $,$ to the slit width, D $,$ as a whole number.

Part $($b$)$

Calculate and enter the ratio of the slit width to the wavelength of the light source.

Part $($c$)$

If the slit separation is $\backslash (27\mathrm{.}2\backslash$mu $\backslash$mathrm$\{$~m$\}\backslash ),$ then calculate and enter the wavelength, in nanometers, of the light source.

Part $($d$)$

What is the slit width, in micrometers?