JEE Advanced 2021 — Paper 2 — Question 9

In a photoemission experiment, the maximum kinetic energies of photoelectrons from metals $\mathrm{P}, \mathrm{Q}$ and R are

$E_{P}, E_{Q}$ and $E_{R}$, respectively, and they are related by $E_{P}=2 E_{Q}=2 E_{R}$. In this experiment, the same source of monochromatic light is used for metal P and Q while a different source of monochromatic light is used for the metal R.The work functions for metals $\mathrm{P}, \mathrm{Q}$ and R are $4.0 \mathrm{eV}, 4.5 \mathrm{eV}$ and 5.5 eV ,

respectively. The energy of the incident photon used for metal $R$, in eV , is $\qquad$ _.