Which of the following alkaline earth metals shows anomalous behavior and has an electronegativity similar to that of aluminum?

$A$ train whistling at a constant frequency is moving towards a station at a constant speed $V_s$. The train goes past a stationary observer on the station. The frequency $n'$ of the sound as heard by the observer is plotted as a function of time $t$. Identify the expected curve.

The figure shows three similar lamps $L_1, L_2$,and $L_3$ connected across a power supply. If the lamp $L_3$ fuses,how will the light emitted by $L_1$ and $L_2$ change?

For the reaction $N_{2(g)} + O_{2(g)} \rightleftharpoons 2NO_{(g)}$,the equilibrium constant $(K_c)$ at temperature $T$ is $4 \times 10^{-4}$. What is the value of $K_c$ for the reaction $NO_{(g)} \rightleftharpoons 1/2 N_{2(g)} + 1/2 O_{2(g)}$ at the same temperature?

During which time interval is the particle described by these position graphs at rest?

Which one of the following population interactions is widely used in medical science for the production of antibiotics?