The wavelength in air associated with a photon of energy E is (c is the speed of light in air and h is the Planck’s constant)


Correct option is

Energy of a photon is E = hv. Now, . Hence  




In Thomson’s experiment for determining , the potential difference between the cathode and the anode (in the accelerating column) is the same as that between the deflecting plates (in the region of crossed fields). If the potential difference is doubled, by what factor should the magnetic field be increased to ensure that the electron beam remains undeflected? 


In Millikan’s oil drop experiment, a charged oil drop of mass  is held stationary between two parallel plates 6 mm apart by applying a potential difference of 1200 V between them. How many excess electrons does the oil drop carry? Take g = 10 ms–2.


In Millikan’s oil drop experiment, an oil drop carrying a charge q falls with a terminal velocity v0 when there is no electric field between the plates. An electric field E is applied to keep it stationary. What additional charge should the oil drop acquire so that it begins to move upwards with a velocity 2v0 in the same electric field?     


A metal whose work function is 3.31 eV is illuminated by light ofwavelength . What is the threshold frequency for photoelectric emission? Take  


What is the maximum energy of photoelectrons emitted from the metal. 


The photoelectric threshold for a certain metal surface is 330 Å. What is the maximum kinetic energy of photoelectron released, if any, by a radiation of wavelength 1100 Å ? 


When a point source of light is at a distance of 50 cm from a photoelectric cell, the cut-off voltage is found to be V0. If the same source is placed at a distance of 1 m from the cell, the cut-off voltage will be 


No photoelectrons are emitted from a metal if the wavelength of light exceeds 6000 Å. The work function of the metal is approximately equal to


The threshold wavelength for photoelectric emission from a material is 5200 Å. photoelectrons will be emitted when this material is illuminated with monochromatic radiation from a


A metal whose work function is 3.3 eV is illuminated by light ofwavelength . What is the threshold frequency for photoelectric emission? Planck’s constant .