For Young's double slit experiment, two statements are given below:
Statement I : If screen is moved away from the plane of slits, angular separation of the fringes remains constant.
Statement II : If the monochromatic source is replaced by another monochromatic source of larger wavelength, the angular separation of fringes decreases.
In the light of the above statements, choose the correct answer from the options given below:
Answer: (C) Statement I is true but Statement II is false.
Angular fringe separation: $\theta = \dfrac{\lambda}{d}$.
Statement I: $\theta$ does not depend on the screen distance $D$. True. (The linear fringe width $\lambda D/d$ changes, but the angular separation does not.)
Statement II: a larger $\lambda$ gives a larger angular separation, not a smaller one. False.
Solution by Sreeraj P, M.Sc Physics