Answer:
The distance between interference fringes increases.
Explanation:
In a double-slit diffraction pattern, the angular position of the nth-maximum in the diffraction patter (measured with respect to the central maximum) is given by
where
is the angular position
is the wavelength
d is the separation between the slits
In this problem, the separation between the slits decreases: this means that d in the formula decreases. As we see, the value of (and so, also
) is inversely proportional to d: so, if the d decreases, then the angular separation between the fringes increases.
So, the correct answer is
The distance between interference fringes increases.