Number of Spectral Lines in He+ Spectrum | JEE Main PYQ | Structure of Atom
Q. Number of spectral lines obtained in He+ spectra, when an electron makes transition from fifth excited state to first excited state will be

Correct Answer: 10

Explanation

For hydrogen-like species, number of spectral lines obtained when an electron transitions from level n₂ to n₁ is:

Number of lines = n(n − 1) / 2

Fifth excited state ⇒ n₂ = 6 First excited state ⇒ n₁ = 2 Total levels involved = 6 − 2 + 1 = 5

Number of spectral lines = 5 × 4 / 2 = 10

Previous Year Questions – Structure of Atom
The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency A × 10¹² hertz and that has a radiant intensity in that direction of 1/B watt per steradian.
Based on Heisenberg's uncertainty principle, the uncertainty in the velocity of the electron to be found within an atomic nucleus of diameter 10⁻¹⁵ m is ____ × 10⁹ m s⁻¹.
Compare the energies of following sets of quantum numbers for multielectron system.
The de-Broglie's wavelength of an electron in the 4th orbit is ____ πa₀.
The maximum number of orbitals which can be identified with n = 4 and mₗ = 0 is ____.
JEE Main Physics – Full Question Bank

Updated for JEE Main 2026: This PYQ is important for JEE Mains, JEE Advanced and other competitive exams. Practice more questions from this chapter.

Scroll to Top