Two thin lenses of focal lengths $f_1$ and $f_2$ are in contact and coaxial. The power of the combination is

At $298 \ K$,the value of $-\frac{\Delta[Br^-]}{\Delta t}$ for the reaction $5 Br^- (aq) + BrO_3^- (aq) + 6 H^+ (aq) \rightarrow 3 Br_2 (aq) + 3 H_2 O (l)$ is $x \ mol \ L^{-1} \ min^{-1}$. What is the rate (in $mol \ L^{-1} \ min^{-1}$) of this reaction?

Explain why $BeH_{2}$ molecule has a zero dipole moment although the $Be-H$ bonds are polar.

Improvement of the human race by improving the environment is called:

The major product of the following reaction is

Beats are produced by two waves given by $y_1 = a \sin(2000 \pi t)$ and $y_2 = a \sin(2008 \pi t)$. The number of beats heard per second is