If a nucleus $P$ converts into a nucleus $Q$ by the decay of one alpha particle and two $\beta^{-}$particles, then the nuclei $P$ and $Q$ are

The graph between the input voltage $\left(V_i\right)$ and the output voltage ( $V_o$ ) of a transistor connected in common emitter configuration is shown in the figure. The active, saturation and cutoff regions of the transistor are respectively

Which of the following logic gates is a universal gate?

The layer of the atmosphere which efficiently reflects high frequency waves particularly at night is