Match List-I with List-II regarding the changes made to a standard...

The angular fringe width in a Young's double slit experiment is given by $\theta = \dfrac{\lambda}{d}$, where $\lambda$ is the wavelength and $d$ is the slit separation. It is independent of the screen distance $D$.

A. Screen moved away from slits: Since $\theta$ does not depend on $D$, the angular fringe width remains constant. (A $\rightarrow$ III)

B. Slit separation is halved: New slit separation $d' = \dfrac{d}{2}$. The new angular width $\theta' = \dfrac{\lambda}{(d/2)} = 2\left(\dfrac{\lambda}{d}\right) = 2\theta$. It becomes double. (B $\rightarrow$ IV)

C. Setup is immersed in a liquid: The wavelength decreases to $\lambda' = \dfrac{\lambda}{1.5}$. Since $\theta \propto \lambda$, the angular fringe width decreases. (C $\rightarrow$ II)

D. Incident light changed from blue to red: The wavelength of red light is greater than that of blue light ($\lambda_{\text{red}} > \lambda_{\text{blue}}$). Since $\theta \propto \lambda$, the angular fringe width increases. (D $\rightarrow$ I)

Therefore, the correct matching is A-III, B-IV, C-II, D-I.

Answer: A-III, B-IV, C-II, D-I