The distance for which ray optics becomes a good approximation for an aperture of 0.3 cm and a light of wavelength $6000 \mathop {\rm{A}}\limits^{\rm{o}}$ is

Match the "Technology" given in List-I with the "Principle of physics" given in List-II.

$$ \begin{array}{l|l|l|l} \hline & \text { List-I (Technology) } & & \text { List-II (Principle of physics) } \\ \hline \text { (A) } & \text { Steam engine } & \text { I } & \begin{array}{l} \text { Magnetic confinement of } \\ \text { plasma } \end{array} \\ \hline \text { (B) } & \text { Electron microscope } & \text { II } & \text { Laws of thermodynamics } \\ \hline \text { (C) } & \text { Non-reflecting coatings } & \text { III } & \text { Wave nature of electrons } \\ \hline \text { (D) } & \text { Tokamak } & \text { IV } & \text { Interference of light } \\ \hline \end{array} $$

When two light waves of equal intensity superimpose, the maximum intensity obtained is $I$. If the intensity of one of the waves is quadrupled, then the maximum intensity obtained is

In Young's double slit experiment, if the distance between 5th bright and 7th dark fringes is 3 mm , then the distance between 5th dark and 7th bright fringes is