If the wavelength of the first line in the Balmer series is $656 \ nm$,then the wavelength of its second line and limiting line respectively are

$A$: Thomson's atomic model is known as the plum pudding model.
$R$: The atom is considered as a positively charged sphere in which electrons are embedded.

An electromagnetic radiation of wavelength $331.5 \ nm$ is made to strike the surface of a metal. Electrons are emitted with a kinetic energy of $1.2 \times 10^5 \ J \ mol^{-1}$. The work function (in $eV$) of the metal is (given: $h=6.63 \times 10^{-34} \ Js$, $N_{A}=6 \times 10^{23} \ mol^{-1}$, $1 \ eV = 1.6 \times 10^{-19} \ J$)?

What is the number of photons of light with a wavelength of $4000 \ pm$ that provide $1 \ J$ of energy?

The time taken for an electron to complete one revolution in Bohr orbit of hydrogen atom is

The threshold frequency $v_{0}$ for a metal is $7.0 \times 10^{14} \,s^{-1}.$ Calculate the kinetic energy of an electron emitted when radiation of frequency $v = 1.0 \times 10^{15} \,s^{-1}$ hits the metal.