In a double-slit interference experiment, assuming that the distance from the location of the double slit to the location of the screen remains fixed, explain what happens to the double-slit interference pattern that appears on the screen if we:
a. increase the wavelength of the laser illuminating a particular, fixed double-slit.
b. decrease the separation of the double-slit (i.e., replace the original double slit witha smaller-separation double-slit) while keeping the illumination unchanged.