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

Atomic spectral emission lines of hydrogen atoms are caused by electron transitions between energy levels. To determine which of these lines can emit photoelectrons from a zinc surface, the energy of the series and their corresponding transitions must be evaluated.

The work function of a material dictates the minimum energy needed to emit photoelectrons. For zinc, this work function is approximately 4.3 eV. Therefore, incident photons must possess energy equal to or exceeding this value to liberate electrons.

Hydrogen's notable spectral series include:

• Lyman Series: Transitions ending at the n=1 energy level. Photon energies for this series start at approximately 10.2 eV (for the n=2 to n=1 transition) and increase. These emissions are in the ultraviolet spectrum.
• Balmer Series: Transitions terminating at the n=2 energy level. These photons possess energies lower than the Lyman series, typically falling within the visible light or near-ultraviolet range. These photon energies are below the work function of zinc.
• Paschen Series: Transitions concluding at the n=3 energy level, emitting infrared radiation with even lower energies.

The Lyman Series, with its sufficiently energetic ultraviolet photons, can overcome the work function of zinc, consequently enabling the emission of photoelectrons.