Category A SYPT QA9: Quantum Light Dimmer If you put a flame with table salt added in front of a vapour sodium lamp, the flame casts a shadow. The shadow can become lighter, if the flame is put into a strong magnetic field. Investigate and explain the phenomenon.

 Category A SYPT QA9: Quantum Light Dimmer  If you put a flame with table salt added in front of a vapour sodium lamp, the flame casts a shadow. The shadow can become lighter, if the flame is put into a strong magnetic field. Investigate and explain the phenomenon.

https://www.youtube.com/watch?v=5ZNNDA2WUSU&t=0s

https://www.youtube.com/watch?v=F0LWtieip9E

https://tmf.fzu.cz/37/pdf/uvodko-17-Nemec.pdf

https://www.youtube.com/shorts/3NO5Z_tD9Nk

https://www.youtube.com/shorts/uUGzrS5tpLc

The phenomenon described involves the interaction of light with atoms in a flame when a magnetic field is present, known as the Zeeman effect. This effect occurs when the energy levels of electrons in atoms are split into sub-levels by the application of a magnetic field. The investigation of this phenomenon with a sodium vapor lamp and a flame containing sodium ions (from table salt) offers a fascinating insight into quantum mechanics and the interaction of light, matter, and magnetic fields. Here’s how to approach an investigation and explanation of this phenomenon:

### Understanding the Phenomenon

1. **Sodium Vapor Lamp**: A sodium vapor lamp emits light primarily at two very close wavelengths in the yellow part of the spectrum (around 589.0 nm and 589.6 nm), corresponding to the transition of electrons in sodium atoms between specific energy levels.

2. **Sodium Flame**: When table salt (sodium chloride, NaCl) is introduced into a flame, sodium atoms are excited to higher energy levels. As these atoms return to their ground state, they emit light at the same characteristic wavelengths as the sodium vapor lamp.

3. **Absorption and Emission**: Normally, the light from a sodium vapor lamp passing through a sodium flame would be absorbed and then re-emitted by the sodium atoms in the flame. Since the emitted light is in all directions, only a part of it continues in the original direction, causing the shadow behind the flame.

4. **Zeeman Effect**: In the presence of a magnetic field, the energy levels of the sodium atoms' electrons are split into several sub-levels due to the Zeeman effect. This splitting alters the absorption and emission characteristics of the atoms.

### Investigating the Effect

1. **Setup**: Place a sodium vapor lamp in such a way that its light passes through a sodium-containing flame and projects onto a screen. Introduce a strong, adjustable magnetic field around the flame using electromagnets.

2. **Observation without Magnetic Field**: Observe the shadow of the flame on the screen without the magnetic field. It should be relatively dark due to the absorption and re-emission process described.

3. **Observation with Magnetic Field**: Gradually increase the magnetic field strength around the flame. Observe changes in the shadow's intensity on the screen.

### Expected Results and Explanation

- **Without Magnetic Field**: The shadow is darker because the sodium atoms in the flame absorb some of the light from the lamp at the sodium's characteristic wavelengths, and the re-emitted light spreads in all directions, with only some of it contributing to the light that reaches the screen.

- **With Magnetic Field**: As the magnetic field strength increases, the energy levels of the electrons in the sodium atoms split into sub-levels (Zeeman effect), causing the absorption lines to broaden or split into multiple components (Zeeman splitting). This splitting can allow more of the lamp's light to pass through the flame without being absorbed, or it alters the absorption/emission pattern enough that more light in the original direction of the lamp reaches the screen, thereby lightening the shadow.

### Factors to Investigate

- **Magnetic Field Strength**: How the intensity of the shadow changes with different strengths of the magnetic field.

- **Flame Composition**: The effect of varying the concentration of sodium in the flame by using different amounts of table salt.

- **Light Wavelengths**: Using filters or spectrometers to observe how specific wavelengths of light are affected by the magnetic field.

### Conclusion

The lightening of the shadow cast by a sodium-containing flame in front of a sodium vapor lamp when subjected to a strong magnetic field is a direct demonstration of the Zeeman effect. This quantum mechanical phenomenon illustrates the interaction between magnetic fields and atomic energy levels, affecting the absorption and emission of light by atoms. By systematically investigating this effect, one can explore fundamental principles of quantum mechanics and electromagnetic interactions in a visually intuitive manner.