Which of the following pairs of transition metal ions have the same calculated values of magnetic moment?

If $f(x) = \sin^2 \left( \frac{\pi}{8} + \frac{x}{2} \right) - \sin^2 \left( \frac{\pi}{8} - \frac{x}{2} \right)$,then the period of $f$ is

$A$ wire of length $l$ is bent into a circular coil of one turn of radius $R_1$. Another wire of the same material,same area of cross-section,and same length is bent into a circular coil of two turns of radius $R_2$. When the same current flows through the two coils,the ratio of magnetic induction at the centres of the two coils is

The principal value of ${\sin ^{ - 1}}\left( { - \frac{1}{2}} \right)$ is

The following compound is used as:

The oxidation states of $S$ atoms in Caro's and Marshall's acids are