Membrane-bound organelles are absent in

Two wires of the same material have lengths in the ratio $1:2$ and their radii are in the ratio $1:\sqrt{2}$. If they are stretched by applying equal forces,the increase in their lengths will be in the ratio:

$A$ Young's double slit experiment uses a monochromatic source. The shape of the interference fringes formed on a screen is

What is the correct order of occurrence ($\%$ by weight) in air of $Ne, Ar$ and $Kr$?

Two concentric coils of $10$ turns each are placed in the same plane. Their radii are $20 \ cm$ and $40 \ cm$ and carry $0.2 \ A$ and $0.3 \ A$ current respectively in opposite directions. The magnetic induction (in $T$) at the centre is

For any integer $n \geq 1$,the sum $\sum_{k=1}^n k(k+2)$ is equal to