The principle of controlled chain reaction is used in

Which of the following pairs is incorrectly matched?

The correct order of second $I.E.$ of $C, N, O$ and $F$ is:

$A$ square matrix $[a_{ij}]$ in which $a_{ij} = 0$ for $i \neq j$ and $a_{ij} = k$ (constant) for $i = j$ is called a

An air column in a tube $32 ~cm$ long,closed at one end,is in resonance with a tuning fork. The air column in another tube,open at both ends,of length $66 ~cm$ is in resonance with another tuning fork. When these two tuning forks are sounded together,they produce $8$ beats per second. Then the frequencies of the two tuning forks are (Consider fundamental frequencies only):

Two cards are drawn successively with replacement from a well-shuffled pack of $52$ cards. The mean of the number of kings is: