In chromite ore,the oxidation number of iron and chromium are respectively

Particles of masses $m, 2m, 3m, \ldots, nm$ grams are placed on the same line at distances $l, 2l, 3l, \ldots, nl$ $cm$ from a fixed point. The distance of the centre of mass of the particles from the fixed point in centimetres is

$A$ compound absorbs light in the wavelength region $490-500 \ nm$. Its complementary colour is

The half-life of a radioactive nucleus is $50 \ days$. The time interval $(t_2 - t_1)$ between the time $t_2$ when $\frac{2}{3}$ of it has decayed and the time $t_1$ when $\frac{1}{3}$ of it has decayed is ......... $days$.

The centre of mass of a system of particles does not depend on:

Which of the following is a disaccharide?