Photons with energy 5 eV are incifent on a cathode C in a photoelectric cell. The maximum energy of emitted photoelectrons is 2 eV. When photons of energy 6 eV are incident on C, no photoelectrons will reach the anode A, if the stopping potential of A relative to C is

Electrons of mass m with de-Broglie wavelength $$\lambda $$ fall on the target in an X-ray tube. The cutoff wavelength ($$\lambda $$₀) of the emitted X-ray is

When a metallic surface is illuminated with radiation of wavelength $$\lambda $$, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2 $$\lambda $$, the stopping potential is $${V \over 4}$$. The threshold wavelength for the metallic surface is

An electron of mass m and a photon have same energy E. The ratio of de-Broglie wavelengths associated with them is