An electron makes a transition from orbit $n = 4$ to the orbit $n = 2$ of the hydrogen atom. The wave number of the emitted radiation ($R =$ Rydberg's constant) will be

If $f(x) = (p - x^n)^{1/n}$,$p > 0$ and $n$ is a positive integer,then $f[f(x)]$ is equal to

If the magnitudes of $a, b$ and $a+b$ are respectively $3, 4$ and $5$, then the magnitude of $(a-b)$ is

Which of the following minerals is not remobilized in plants?

When the engine is switched off,a vehicle of mass $M$ is moving on a rough horizontal road with momentum $p$. If the coefficient of friction between the road and the tyres of the vehicle is $\mu_k$,what is the distance travelled by the vehicle before it comes to rest?

In which of the following reactions does the hybridisation of the central atom change from $sp^2$ to $sp^3$?