Radiations of wavelength 400 nm incidents on a photosensitive material of work function 2.2 eV . The stopping potential is nearly

Consider two black bodies $A$ and $B$ having equal surface area. On the surface of $A, n$ photons of frequency $f$ are incident perpendicularly in a time $t$. On the surface of $B$, $2 n$ photons of frequency $3 f$ are incident perpendicularly in a time $4 t$. The ratio of average intensity of radiation on surface $A$ to that on surface $B$ is

A photon released by the transition of an electron from the second excited state to the ground state of Hydrogen atom is incident on the surface of a metal of work function 3.1 eV . The de-Broglie wavelength of the most energetic electron emitted from that metal surface is nearly

The de-Broglie wavelength of a particle moving with a speed of $0.8 c$ is equal to the wavelength of a photon. If $c$ is speed of the photon in vacuum, the ratio of the energy of the photon and the kinetic energy of the particle is