The work function of Cu is $7.68 \times 10^{-19} \mathrm{~J}$. If photons of wavelength 221 nm are made to strike the surface of the metal, the kinetic energy (in J) of the ejected electrons will be ( $h=6.63 \times 10^{-34} \mathrm{Js}$ )

In an element with atomic number $(Z) 25$, the number of electrons with $(n+l)$ value equal to 3 and 4 are $x$ and $y$ respectively. The value of $(x+y)$ is

The wavelength of a particular electron transition for $\mathrm{He}^{+}$is 100 nm . The wavelength (in $\AA$ ) of H atom for the same transition is

The energy of second Bohr orbit of hydrogen atom is -3.4 eV . The energy of the fourth Bohr orbit of the $\mathrm{He}^{+}$ ion will be