The isoelectronic set of ions is:

A $50$ watt bulb emits monochromatic red light of wavelength of $795 \mathrm{nm}$. The number of photons emitted per second by the bulb is $x\times {10}^{20}.$ The value of $x$ is _____ .

(Nearest integer)

$\text{ [Given : }\left.\mathrm{h}=6.63\times {10}^{-34}\mathrm{Js}\text{ and} \mathrm{c}=3.0\times {10}^8 {\mathrm{ms}}^{-1}\right]$

Consider the following pairs of electrons:

(A) (a) $\mathrm{n}=3, \mathrm{l}=1, {\mathrm{m}}_{\mathrm{l}}=1,{\mathrm{m}}_{\mathrm{s}}=+\frac{1}{2}$
(b) $\mathrm{n}=3, \mathrm{l}=2,{\mathrm{m}}_{\mathrm{l}}=1,{\mathrm{m}}_{\mathrm{s}}=+\frac{1}{2}$
(B) (a) $\mathrm{n}=3, \mathrm{l}=2,{\mathrm{m}}_{\mathrm{l}}=-2,{\mathrm{m}}_{\mathrm{s}}=-\frac{1}{2}$
(b) $\mathrm{n}=3, \mathrm{l}=2,{\mathrm{m}}_{\mathrm{l}}=-1,{\mathrm{m}}_{\mathrm{s}}=-\frac{1}{2}$
(C) (a) $\mathrm{n}=4, \mathrm{l}=2,{\mathrm{m}}_{\mathrm{l}}=2,{\mathrm{m}}_{\mathrm{s}}=+\frac{1}{2}$
(b) $\mathrm{n}=3,\mathrm{l}=2,{\mathrm{m}}_{\mathrm{l}}=2,{\mathrm{m}}_{\mathrm{s}}=+\frac{1}{2}$

The pairs of electrons present in degenerate orbitals is/are:

The longest wavelength of light that can be used for the ionisation of lithium atom $\left(\mathrm{Li}\right)$ in its ground state is $\mathrm{x}\times {10}^{-8} \mathrm{m}$. The value of $\mathrm{x}$ is (Nearest Integer)

(Given : Energy of the electron in the first shell of the hydrogen atom is $-2.2\times {10}^{-18} \mathrm{J}$; $\mathrm{h}=6.63\times {10}^{-34}\mathrm{Js}$ and $\mathrm{c}=3\times {10}^8{ \mathrm{ms}}^{-1}$)

The minimum energy that must be possessed by photons in order to produce the photoelectric effect with platinum metal is:

[Given: The threshold frequency of platinum is $1.3\times {10}^{15}{ \mathrm{s}}^{-1}$ and $\mathrm{h}=6.6\times {10}^{-34}\mathrm{Js}$]