In YDSE , what should be the width of each slit to obtain 20 maxima of the double slit pattern within the central maximum of the single slit pattern ? (d=1mm)

Explanation

We want `theta=lamda/d(n=1)`
Now `20 lamda/d=2 lamda/a`
`implies a=d/10=0.1 mm`
It is interesting to note that wavelength of light and distance of the screen do not take part in the calculation of a.