A gas can be too cold to absorb Balmer series lines. Is this also true for the Panchen series? (See Figure 7.5.) for the Lyman series? Explain.

Paschen series is a sequence of emission or absorption lines along the infrared part of hydrogen atom. It is caused by the movement of electron between 3^rd energy level and the higher levels

The Lyman series is a series of ultraviolet spectrum lines of atomic hydrogen between 122 and 91 nanometres.

A gas can be too cold to absorb wavelengths of light belonging to the Balmer series because the transitions involve the electron being initially in the n = 2 excited state and absorbing a photon to change to a higher excited state, and the Balmer series transitions will not be observed.

The Paschen series results from transitions in which the atom is initially in its ground state. Because the ground state is populated no matter how cold the gas is, so it can always absorb wavelengths belonging to the Paschen series.

Absorption lines, in the Lyman series result from transitions in which the atom is initially in the n = 3 excited state and here too if the gas is too cold the n = 3 state is not populated and the absorption transition in the Lyman series cannot occur.

Thus, it is true for Paschen series but not true for Lyman series.