JEE Advanced 2023 — Paper 1 — Question 24

A Hydrogen-like atom has atomic number Z. Photons emitted in the electronic transitions from level $\mathrm{n}=4$ to level $n=3$ in these atoms are used to perform photoelectric effect experiment on a target metal. The maximum kinetic energy of the photoelectrons generated is 1.95 eV . If the photoelectric threshold wavelength for the target metal is 310 nm , the value of Z is [0pt] [Given: hc $=1240 \mathrm{eV}-\mathrm{nm}$ and $\mathrm{Rhc}=13.6 \mathrm{eV}$, where R is the Rydberg constant, h is the Planck's constant and $c$ is the speed of light in vacuum]