Two identical photocathodes receive light of frequencies ' $f 1$ ' and ' $f_2$ '. The velocity of the photoelectrons of mass ' $m$ ' emitted are respectively ' $\mathrm{v}_1$ ' and ' $\mathrm{v}_2$ '. Then the correct relation is ( $\mathrm{h}=$ Planck's constant)

A photon and an electron have equal energy ' $E$ '. The ratio of wavelength of photon to wavelength of electron is proportional to

The energy of a photon is equal to the kinetic energy of proton. If $\lambda_1$ is the de-Broglie wavelength of a proton, $\lambda_2$ is the wavelength associated with the photon and if E is the energy of photon then $\lambda_2: \lambda_1$ is

The work function of a photosensitive metallic surface is $h v_0$. If photons of energy (2.5) $h v_0$ fall on this surface, the electrons come out with maximum velocity ' v '. When the photon energy is increased to $7 \mathrm{~h} v_0$, the maximum velocity of photoelectrons will be