The gold numbers of $A$,$B$,$C$,and $D$ are $0.04$,$0.002$,$10$,and $25$ respectively. The protective power of $A$,$B$,$C$,and $D$ are in the order:

Two beams of light having intensities $I$ and $4I$ interfere to produce a fringe pattern on a screen. The phase difference between the beams is $\pi / 2$ at point $A$ and $\pi$ at point $B$. Then the difference between the resultant intensities at $A$ and $B$ is (in $I$)

In a Ruby laser, the colour of laser light is due to ______ atom.

$A$ transformer works on the principle of

Which of the following produces hydrolith with dihydrogen?

Vessels and Companion cells are characteristics of