Which of the following curve represents the speed of the electron in…

The correct answer is Option (1)

In the Bohr model the speed of the electron in the \( n \)th orbit is

    \( \displaystyle v_n = \frac{e^{2}}{2\varepsilon_0 h}\,\frac{Z}{n} \;\Rightarrow\; v \propto \frac{1}{n} \)

So the speed falls as \( n \) increases, and the graph of \( v \) against \( n \) is a rectangular hyperbola: steep at small \( n \), flattening out and approaching the \( n \)-axis without reaching it. Option (1) shows this curve.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), but it is still in the CUET 2026 syllabus, so do not skip it.

NCERT (Pre-rationalised edition, 2022-23):
Bohr Model of the Hydrogen Atom – “… Combining it with Eq. (12.13), we get the following expressions for v_n and r_n,

    \( \displaystyle v_n = \frac{1}{n}\frac{e^2}{4\pi\varepsilon_0}\frac{1}{(h/2\pi)} \qquad (12.14) \)

… Eq. (12.14) depicts that the orbital speed in the nth orbit falls by a factor of n.”