A light wave of wavelength $$\lambda$$ is incident on a slit of width $$d$$. The resulting diffraction pattern is observed on a screen at a distance $$D$$. If linear width of the principal maxima is equal to the width of the slit, then the distance $$D$$ is

When wavelength of light used in optical instruments A and B are 4500$$\mathop A\limits^o $$ and 6000$$\mathop A\limits^o $$ respectively, the ratio of resolving power of A to B will be

In diffraction experiment, from a single slit, the angular width of the central maxima does not depend upon

In Young's double slit experiment green light is incident on the two slits. The interference pattern is observed on a screen. Which one of the following changes would cause the observed fringes to be more closely spaced?