For a $H$-atom,what is the wavelength in $nm$ associated with the transition of an electron from an infinite energy level to the first energy level? (Rydberg constant = $1.097 \times 10^{7} \ m^{-1}$)

The threshold frequency of a metal is $10^{15} \ s^{-1}$. The ratio of maximum kinetic energies of the photoelectrons, when the metal is irradiated with radiations of frequencies $1.5 \times 10^{15} \ s^{-1}$ and $2.0 \times 10^{15} \ s^{-1}$ respectively, is

Time taken for an electron to complete one revolution in the Bohr orbit of hydrogen atom is

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 will be the energy of an electron emitted from the ground state to the $n^{th}$ orbit?

In which of the following transitions is a photon of maximum energy absorbed?