The peak emission from a block body at a certain temperature occurs at a wavelength of 6200A0. On increasing its temperature, the total radiation emitted is increased 16 times. These radiations are allowed to fall on metal surface. Photoelectrons emitted by the peak radiation at higher temperature can be brought to rest by applying a potential equivalent to the excitation potential corresponding to the transition for the level n=4 to n=2 in the Bohr’s hydrogen atom. The work function of the metal is given by α 100 eV where α is the numerical constant. Find the value of α/29 . (Round off to nearest integer)

Question

The peak emission from a block body at a certain temperature occurs at a wavelength of 6200A0. On increasing its temperature, the total radiation emitted is increased 16 times. These radiations are allowed to fall on metal surface. Photoelectrons emitted by the peak radiation at higher temperature can be brought to rest by applying a potential equivalent to the excitation potential corresponding to the transition for the level n=4 to n=2 in the Bohr’s hydrogen atom. The work function of the metal is given by α 100 eV  where α  is the numerical constant. Find the value of  α/29  . (Round off to nearest integer)

Accepted Answer

Radiation α T 4   So =2 T 1  and By Wein's displacement law λα 1 T  So λ2=λ12=3100A∘ By Einstein’s photoelectric equation  hc λ=eV+ϕϕ=hc λ−eV=hc 3100A∘−(13.6eV)12122−142=4.00−2.55ϕ=1.45ev=1.45=α100or α=145

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