Given below are two statements: one is labelled as Assertion (A)...

The linear fringe width in Young's double slit experiment is given by $\beta = \dfrac{\lambda D}{d}$, where $\lambda$ is the wavelength, $D$ is the distance to the screen, and $d$ is the slit separation.

The angular fringe width is given by $\theta = \dfrac{\beta}{D} = \dfrac{\lambda}{d}$.

When the screen is moved away from the plane of the slits, the distance $D$ increases. This causes the linear fringe width $\beta$ to increase. However, the angular fringe width $\theta$ depends only on $\lambda$ and $d$, so it remains independent of $D$.

Therefore, both Assertion (A) and Reason (R) are correct, and Reason (R) provides the correct explanation for Assertion (A).

Answer: Both Assertion (A) and Reason (R) are correct and Reason (R) is the correct explanation for Assertion (A).