The minimum energy needed to remove an electron from a metal corresponds to a wavelength of 500 nm . What is the total kinetic energy of all the photoelectrons ejected per second when the entire radiation from a 100 Watt bulb with a wavelength of 300 nm falls on the surface of the metal? [Planck's constant $=6.6 \times 10^{34} \mathrm{Js}$; speed of light $=3 \times 10^8 \mathrm{~ms}^{-1}$ ]

Which of the following expressions represents the hydrogen atom wave function $\psi(r)$ shown in the figure below? ( $r$ is the distance of the electron from the nucleus and $a_0$ is a constant)

The total number of nodes for a given principal quantum number $n$, and azimuthal quantum number $\ell$, are