Question

The figure indicates the energy level diagram of an atom and the origin of six spectral lines in emission (e.g. line no. 5 arises from the transition from level B to A). Which of the following spectral lines will occur in the absorption spectrum?

• A. 4,5,6
• B. 1,2,3,4,5,6
• C. 1,2,3
• D. 1,4,6.

Answer 1

The Correct Option is A

To determine which spectral lines will occur in the absorption spectrum, we must understand the difference between emission and absorption spectra.

In an emission spectrum, electrons transition from higher energy levels to lower ones, emitting photons of specific energies as they move closer to the nucleus. In contrast, an absorption spectrum occurs when electrons absorb energy and move from a lower energy level to a higher energy level. Therefore, the spectral lines in an absorption spectrum are associated with upward transitions from a lower energy level to a higher one.

Given that the question indicates transitions that result in emission of spectral lines (for example, line 5 is a transition from level B to A), the absorption spectrum would involve the reverse transitions: from level A to level B, and so on.

Considering all the lines:

• Lines 4, 5, and 6 correspond to transitions to lower energy levels (i.e., emitted spectra). In the absorption spectrum, these would appear as upward transitions.
• Lines 1, 2, 3 signify transitions from higher to lower levels and their reverse transitions would appear in absorption.

Thus, the lines that will occur in the absorption spectrum must be the reverse of those found in emission spectra, which implies 4, 5, and 6.

Therefore, the correct option is 4,5,6, where these lines will appear in the absorption spectrum as they represent transitions where electrons absorb energy to move to higher energy levels.