Question

Atomic spectral emission lines of hydrogen atom are incident on a zinc surface. The lines which can emit photoelectrons from the surface are members of:

• A. Balmer series
• B. Paschen series
• C. Lyman series
• D. Neither Balmer, nor Paschen nor Lyman series

Hint:

Only photons with energy greater than the work function of the material can cause the emission of photoelectrons.

Answer 1

The Correct Option is C

The atomic spectral emission lines of a hydrogen atom relate to electronic transitions between energy levels. The key to determining which of these can emit photoelectrons from a zinc surface involves evaluating the series and their corresponding energies: 

The energy required to emit photoelectrons from a surface is determined by the work function of the material. For zinc, this work function is approximately 4.3 eV. Thus, incident photons must have energy equal to or greater than this value to release electrons.

In hydrogen, the significant spectral series include:

• Lyman Series: Transitions to the n=1 level. The energy of these photons ranges from approximately 10.2 eV (for n=2 to n=1) to higher energies. These are in the ultraviolet range.
• Balmer Series: Transitions to the n=2 level, with energies less than Lyman, typically considered visible light or near ultraviolet. These photons have energies less than the zinc work function.
• Paschen Series: Transitions to the n=3 level, emitting infrared radiation with even lower energies.

The Lyman Series involves sufficiently energetic ultraviolet photons that can surpass the work function of zinc and thus can emit photoelectrons.