In good conductors of electricity,the type of bonding that exists is

The wavelengths of $K_{\alpha}$ $X$-rays of two metals $A$ and $B$ are $\frac{4}{1875R}$ and $\frac{1}{675R}$ respectively,where $R$ is the Rydberg constant. The number of elements lying between $A$ and $B$ according to their atomic numbers is:

If the number of $5$-element subsets of the set $A = \{a_1, a_2, \ldots, a_{20}\}$ of $20$ distinct elements is $k$ times the number of $5$-element subsets containing $a_4$,then $k$ is

$A$ block of mass $M_1$ is hung by a light spring of force constant $k$ from the top bar of a reverse $U$-frame of mass $M_2$ resting on the floor. The block is pulled down from its equilibrium position by a distance $x$ and then released. The minimum value of $x$ such that the reverse $U$-frame will leave the floor momentarily is:

Consider the general reaction given below at $400 \ K$: $xA_{(g)} \rightleftharpoons yB_{(g)}$. The values of $K_p$ and $K_c$ are studied under the same condition of temperature but variation in $x$ and $y$. $(i)$ $K_p = 85.87$ and $K_c = 2.586$ (appropriate units). $(ii)$ $K_p = 0.862$ and $K_c = 28.62$ (appropriate units). The values of $x$ and $y$ in $(i)$ and $(ii)$ respectively are:

Two coherent sources whose intensity ratio is $64: 1$ produce interference fringes. The ratio of intensities of maxima and minima is