Q24 (c)

Criteria	Marks
Explains the physical processes that result in the absorption spectrum	3
Outlines some aspects of physical processes involved in the production of an absorption spectrum	2
Provides some relevant information	1

Sample answer: The star produces a continuous spectrum of light. When this light passes through the hydrogen atmosphere, certain frequencies of light are absorbed as they have energies (from $E = hf$) that correspond to particular transitions of electrons to higher energy levels. Such frequencies produce wavelengths that do not progress through the atmosphere, and as a result show as a drop in intensity on the graph.

Answers could include: Absorption spectron of non-stellar origin