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  • Consider a singly ionized helium atom. The wavelengths  can be emit

Consider a singly ionized helium atom. The wavelengths (\stackrel{\circ}{\boldsymbol{A}}) can be emitted when these atoms in the ground state are bombarde by electrons that have been accelerated through a potential difference of 50 \mathrm{~V} is

Option: 1

1645 \mathrm{~A}^{\circ}


Option: 2

257 \mathrm{~A}^{\circ}


Option: 3

304\, \, \AA


Option: 4

All of the above


Answers (1)

best_answer

Energy of the electron accelerated through a potential difference of 50 V
is 50eV

At most, it can excite electron fron n=1 to n=3

The number of possible wavelength are 3

\frac{1}{\lambda}=\frac{54.4 \times 1.6 \times 10^{-19}}{h c}\left[\frac{1}{n_1^2}-\frac{1}{n_2^2}\right]

For transition 3-2, \mathrm{n}_1=2, \mathrm{n}_2=3 . 

          \lambda_{32}=1645 \mathrm{~A}^{\circ}

For 3-1 ; n_1=1 ; n_2=3

\lambda_{31}=257 \mathrm{~A}^{\circ}

For 2-1 ; \mathrm{n}_1=1 ; \mathrm{n}_2=2

\lambda_{21}=304 \mathrm{~A}^{\circ}

Posted by

Suraj Bhandari

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