When wavefronts pass from denser medium to rarer medium, the width of the wavefront

A diffraction pattern is obtained using a beam of red light. If red light is replaced by blue light then

The intensity ratio of the maxima and minima in an interference pattern produced by two coherent sources of light is $9: 1$. The intensities of the light sources used are in the ratio

Two points separated by a distance of 0.1 mm can just be seen in microscope when light of wavelength $6000 \mathop A\limits^o $ is used. If the light of wavelength $4800 \mathop A\limits^o $ is used, the limit of resolution will become