An element playing an important role in nitrogen fixation is

$A$ very small hole in an electric furnace is used for heating metals. The hole nearly acts as a black body. The area of the hole is $200 ~mm^2$. To keep a metal at $727^{\circ} C$,the heat energy flowing through this hole per second,in joules,is $\left(\sigma = 5.67 \times 10^{-8} ~W m^{-2} K^{-4}\right)$.

Which of the following compounds exhibits optical isomerism?

What is the correct order of stability for the superoxides?

Which of the following is paramagnetic?

Two bodies $A$ and $B$ of equal surface area have thermal emissivities of $0.01$ and $0.81$ respectively. The two bodies are radiating energy at the same rate. Maximum energy is radiated from the two bodies $A$ and $B$ at wavelengths $\lambda_A$ and $\lambda_B$ respectively. The difference in these two wavelengths is $1 \mu m$. If the temperature of the body $A$ is $5802 \ K$,then the value of $\lambda_B$ is: