To determine which spectral lines will not occur in the absorption spectrum, we need to consider the transitions that are possible based on the energy level diagram provided. In absorption, electrons are promoted from lower energy levels to higher ones, resulting in absorption lines corresponding to these transitions.
Looking at the diagram:
Absorption can occur for transitions from lower to higher energy levels.
The lines that won't occur in the absorption spectrum are those where there are no higher energy levels to transition to.
Based on this, let's analyze each option:
(a) 1, 2, 3: Lines 1, 2, and 3 all have higher energy levels available for absorption (C, D, and E respectively), so they could occur in the absorption spectrum. This option is not correct.
(b) 3, 2: Line 3 has a higher energy level (E) available for absorption, but Line 2 doesn't have a higher energy level to transition to (only transitions to lower energy levels). So, Line 2 would not occur in the absorption spectrum. This option could be correct.
(c) 4, 5, 6: Lines 4, 5, and 6 all have higher energy levels available for absorption (A, B, and C respectively), so they could occur in the absorption spectrum. This option is not correct.
(d) 3, 2, 1: Line 1 doesn't have a higher energy level to transition to, so it wouldn't occur in the absorption spectrum. However, Lines 2 and 3 do have higher energy levels available for absorption (D and E respectively), so they could occur in the absorption spectrum. This option is not correct.
So, the correct answer is:
(b) 3, 2
