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Question : 8
Total: 27
A photon emitted during the de-excitation of electron from a state n to the first excited state in a hydrogen atom, irradiates a metallic cathode of work function 2 eV , in a photo cell, with a stopping potential of 0.55 V . Obtain the value of the quantum number of the state n .
OR
A hydrogen atom in the ground state is excited by an electron beam of12.5 eV energy. Find out the maximum number of lines emitted by the atom from its excited state.
OR
A hydrogen atom in the ground state is excited by an electron beam of
Solution:
● For writing Einstein's photoelectric equation
● For writing,E n = −
● For finding the value ofn
From photoelectric equation,h v = ϕ 0 + e V s
= 2 + 0.55 = 2.55 eV
Given,E n =
The energy difference
∆ E = − 3.4 − ( − 2.55 ) eV = − 0.85 eV
∴
= − 0.85
∴ n = 4
OR
Calculation of energy in excited state Formula
Finding out the maximum number of lines.
Energy in ground state,E 1 = − 13.6 eV
Energy supplied= 12.5 eV
Energy in excited state,− 13.6 + 12.5 = − 1.1 eV
But,E n =
= − 1.1
n = 3
Maximum number of lines= 3
● For writing,
● For finding the value of
From photoelectric equation,
Given,
The energy difference
OR
Calculation of energy in excited state Formula
Finding out the maximum number of lines.
Energy in ground state,
Energy supplied
Energy in excited state,
But,
Maximum number of lines
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