If the threshold wavelength of light for photoelectric emission to take place from a metal surface is $6250 \mathop {\rm{A}}\limits^{\rm{o}}$, then the work function of the metal is (Planck's constant $=6.6 \times 10^{-34} \mathrm{Js}$ )

A camera is fabricated using a semiconducting material having a band gap of 3 eV . The wavelength of light if can detect is nearly

If the linear momentum of a proton is changed by $p_0$ then the de-Broglie wavelength associated with the proton changes by $0.25 \%$. Then the initial linear momentum of the proton is

If an electron in the excited state falls to ground state, a photon of energy 5 eV is emitted, then the wavelength of the photon is nearly