An important evidence in favour of organic evolution is the occurrence of

When a mass $m$ is connected individually to two springs $S_1$ and $S_2$,the oscillation frequencies are $v_1$ and $v_2$. If the same mass is attached to the two springs as shown in the figure,the oscillation frequency would be

If ${z_r} = \cos \frac{{r\alpha }}{{{n^2}}} + i\sin \frac{{r\alpha }}{{{n^2}}},$ where $r = 1, 2, 3, \dots, n$,then $\mathop {\lim }\limits_{n \to \infty } \,{z_1}{z_2}{z_3}\dots{z_n}$ is equal to

The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is

$2 \ mol$ of zinc is dissolved in $HCl$ at $25 \ ^\circ C$. The work done in an open vessel is: