Plants adapted to low light intensity have

The curve between charge density and distance near a $P-N$ junction will be:

$A$ metal is burnt in air and the ash on moistening smells of $NH_3$. The metal is

The velocities of three particles of masses $20 \ g$,$30 \ g$,and $50 \ g$ are $10 \hat{i}$,$10 \hat{j}$,and $10 \hat{k}$ respectively. The velocity of the centre of mass of the three particles is:

Let $k$ be a non-zero real number. If $f(x) = \begin{cases} \frac{(e^x - 1)^2}{\sin(\frac{x}{k}) \log(1 + \frac{x}{4})} & x \neq 0 \\ 12 & x = 0 \end{cases}$ is a continuous function,then the value of $k$ is: