When an electron drops from a higher energy level to a lower energy level,then

The energy level for $A^{(+z-1)}$ is given by which of the following expressions?

The work function for a metal is $4 \, eV$. To emit a photo electron of zero velocity from the surface of the metal,the wavelength of incident light should be : ................ $\mathring{A}$

$A$ bulb emits electromagnetic radiation of $660 \, nm$ wavelength. The total energy of radiation is $3 \times 10^{-18} \, J$. The number of emitted photons will be :
$(h = 6.6 \times 10^{-34} \, J \cdot s, \, c = 3 \times 10^{8} \, m/s)$

The maximum wavelength of radiation that can ionise a sodium atom is $2414 \ \mathring{A}$. The ionisation energy of sodium per mole shall be

When an electron jumps from $n = 5$ to $n = 2$ with all possible transitions,which of the following statements is correct?