The number of nuclei of a radioactive substance at time $t = 0$ is $1000$,and at time $t = 2 \ s$,it is $900$. Then,the number of nuclei at time $t = 4 \ s$ will be:

On adding $AgNO_3$ solution into $KI$ solution,a negatively charged colloidal sol is obtained when they are in:

If $p \rightarrow (\sim p \vee q)$ is false,then the truth values of $p$ and $q$ are respectively

$A$ light ray of wavelength $\lambda$ is passing through a pinhole of diameter $D$ and the effect is observed on a screen placed at a distance $L$ from the pinhole. The approximations of geometrical optics are applicable,if

If the values of $\Lambda_{\infty}$ of $NH_4Cl, NaOH$ and $NaCl$ are $130, 217$ and $109 \ \Omega^{-1} \ cm^2 \ equiv^{-1}$ respectively,the $\Lambda_{\infty}$ of $NH_4OH$ in $\Omega^{-1} \ cm^2 \ equiv^{-1}$ is

$A$ plane passes through the point $A(2, 1, -3)$. If the distance of this plane from the origin is maximum,then its equation is: