Stopping potential =4.2−1.5=2.7VPhotoelectron emission will stop, if the potential of the sphere reaches the stopping potential. Let the charge on sphere be q when photoelectron emission stopsso 2.7= 0.1kq​ →q=3×10 −11 CNow n=q/e , n=1.875×10 8

A source of light is placed above a sphere of radius 10cm. How many photoelectrons must be emitted by the sphere before emission of photoelectrons stops? The energy of incident photon is 4.2 eV and the work function of the metal is 1.5 eV.

The electron in the hydrogen atom jumps from excited state (n=3) to its ground state (n=1) and the photons thus emitted irradiate a photosensitive material. If the work function of the material is 5.1eV, the stopping potential is estimated to be

The maximum kinetic energy of photoelectrons emitted from a surface when photons of energy 6 eV fall on it is 4 eV. The stopping potential in volts is :

If maximum velocity with which an electron can be emitted from a photo cell is 4 × 108 cm/s, the stopping potential is (mass of electron = 9 × 10–31 kg)

A container consists of a sample of hydrogen like ions all of which are in the same state. In this state, ionization energy of an ion is 36 of ionization energy of hydrogen atom. This sample is now allowed to reach its most stable configuration, thereby resulting in 10 distinct types of photons. The most energetic Paschen-line photons from this sample are made incident on a metal. The stopping potential of the ejected photoelectrons is observed to be  3.704 V. Find the work function of the target (in eV) to the nearest integer.