Final answer:
The Zeeman effect measures changes in energy levels within an atom by observing the splitting of spectral lines when an external magnetic field is applied. This splitting is proportional to the strength of the magnetic field and allows for precise measurement of magnetic fields, including those on the Sun's surface.
Step-by-step explanation:
Measuring Change in Energy: Zeeman Effect
To measure the change in energy due to the Zeeman effect using a magnetic field, you first apply an external magnetic field to an atom and then observe the induced splitting of its spectral lines. The Zeeman effect causes the splitting of these lines due to transitions from higher to lower energy states.
For example, transitions from the state (n = 2, l = 1) to a lower energy state result in three closely spaced spectral lines, and transitions from the state (n = 2, l = 2) result in five lines, as the separation of these lines is proportional to the strength of the external magnetic field.
When you increase the strength of the magnetic field (Bext), the spectral lines exhibit greater splitting. This proportional relationship allows for precise measurements of magnetic fields, such as those found in sunspots on the surface of the Sun.
These measurements led to the creation of a magnetogram—a map of magnetic activity. Moreover, it is important to note that in the absence of an external magnetic field, spectral lines can still appear split due to internal magnetic fields within the atom itself.