Question

The maximum number of emission lines for atomic hydrogen that you would expect to see with naked eye if the only electronic levels involved are those shown in the figure, is

A. 6
B. 5
C. 21
D. \[\infty \]

Answer 1

Hint:Recall the basics of the emission spectrum of an atomic hydrogen. Check out of the all series obtained in the emission spectrum of the hydrogen atom, emission lines from which series can be seen with the naked eye. Also check the in which energy level the electron transitions should take place to obtain the naked emission lines in the Balmer series.

Complete answer:
We have asked to determine the number of the emission lines for the atomic hydrogen that one can see with the naked eye if the only number of electronic levels involved in the transition are shown in the figure.We have given there are 7 electronic levels in the spectrum of the hydrogen atom.One can see the emission lines for the transition of electron only if the transition lines lies in the visible region.

We know that out of the all transition series obtained by the transition of electron, only the transition lines in the Balmer series lies in the visible region.The transition lines from the Balmer series are obtained when the electron undergoes transition from the higher energy levels to the second energy level called \[n = 2\].

From the given atomic hydrogen spectrum, we can see that the electrons from the energy levels named \[n = 3\], \[n = 4\], \[n = 5\], \[n = 6\] and \[n = 7\] can undergo transition to give emission lines in Balmer series.The transitions giving the emission lines that can be seen with the naked eyes are \[3 \to 2\], \[4 \to 2\], \[5 \to 2\], \[6 \to 2\] and \[7 \to 2\]. Therefore, there are 5 emission lines in the given spectrum of the atomic hydrogen that can be seen with the naked eye.

Hence, the correct option is B.

Note: The students should keep in mind that not all the emission lines in the Balmer series can be seen with the naked eye. This is because not all the transitions in the Blamer series lie in the visible region. There are only four lines that are in the visible region. The remaining emission lines lie in the ultraviolet and other regions of the spectrum.