Coherent red light illuminates two narrow slits that are 25 cm apart.?

Question

Will a two-slit interference pattern be observed when the light from the slits falls on a screen? Explain.

Answer 1

Did you really mean 25 cm? The pattern will be there, but not observed. There will be something like a million lines on a 180-degree screen. This is because a 1-wavelength path difference between the two slits corresponds to about a 3-microradian spacing; i.e., theta = lambda/d. See the ref.