# Étienne-Louis Malus

> French officer, engineer, physicist, and mathematician (1775-1812)

**Wikidata**: [Q315391](https://www.wikidata.org/wiki/Q315391)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Étienne-Louis_Malus)  
**Source**: https://4ort.xyz/entity/etienne-louis-malus

## Summary
Étienne-Louis Malus was a French officer, engineer, physicist, and mathematician best known for his contributions to optics, particularly the discovery of the polarization of light by reflection, now known as Malus' law. His work laid foundational principles in the study of light and influenced the development of modern optical physics.

## Biography
- **Born**: July 23, 1775
- **Died**: February 24, 1812
- **Nationality**: French
- **Education**: École royale du génie de Mézières, École polytechnique
- **Known for**: Discovering the polarization of light by reflection and formulating Malus' law
- **Employer(s)**: French Armed Forces
- **Field(s)**: Optics, physics, mathematics, engineering

## Contributions
Étienne-Louis Malus made significant contributions to the field of optics. His most notable discovery was the polarization of light by reflection, which he documented in 1808. This discovery led to the formulation of Malus' law, which describes the intensity of light transmitted through a polarizer. His work provided a fundamental understanding of how light behaves when reflected off surfaces, influencing subsequent research in optical physics. Additionally, Malus participated in several military campaigns during the Napoleonic Wars, including the Battle of the Nile and the Battle of the Pyramids, showcasing his dual role as a scientist and military officer.

## FAQs
**What is Malus' law?**
Malus' law describes the intensity of polarized light after it passes through a polarizer. It states that the intensity of the transmitted light is proportional to the square of the cosine of the angle between the polarization direction of the incident light and the transmission axis of the polarizer.

**Where did Étienne-Louis Malus receive his education?**
Malus studied at the École royale du génie de Mézières and later at the École polytechnique, two prestigious institutions in France known for their rigorous training in engineering and mathematics.

**What military campaigns did Étienne-Louis Malus participate in?**
Malus was involved in several key battles during the Napoleonic Wars, including the Battle of the Nile (1798), the Battle of the Pyramids (1798), and the Siege of Jaffa (1799). His military service was intertwined with his scientific pursuits.

**What awards or recognitions did Étienne-Louis Malus receive?**
Malus was honored with the Rumford Medal, awarded by the Royal Society for his contributions to the study of light and optics. His name is also inscribed on the Eiffel Tower among the 72 names of scientists, engineers, and industrialists who honored France from 1789 to 1889.

## Why They Matter
Étienne-Louis Malus' work on the polarization of light revolutionized the field of optics, providing a mathematical framework for understanding how light interacts with surfaces. His discoveries laid the groundwork for advancements in optical technologies, including the development of polarizing filters and other optical instruments. Malus' dual career as a military officer and scientist also highlights the intersection of practical engineering and theoretical physics during his time. Without his contributions, the study of light and its applications in modern technology would have progressed more slowly.

## Notable For
- Discovering the polarization of light by reflection
- Formulating Malus' law, a fundamental principle in optics
- Participating in key battles during the Napoleonic Wars
- Receiving the Rumford Medal for his contributions to optics
- Having his name inscribed on the Eiffel Tower as one of France's honored scientists

## Body
### Early Life and Education
Étienne-Louis Malus was born on July 23, 1775, in France. He pursued his education at the École royale du génie de Mézières, a renowned military academy, and later at the École polytechnique, where he honed his skills in engineering and mathematics. These institutions provided him with a strong foundation in both theoretical and applied sciences, which would later influence his contributions to optics and physics.

### Military Career
Malus served as an officer in the French Armed Forces and participated in several significant military campaigns during the Napoleonic Wars. His involvement in battles such as the Battle of the Nile (1798), the Battle of the Pyramids (1798), and the Siege of Jaffa (1799) showcased his dedication to both military service and scientific inquiry. His experiences in these campaigns likely influenced his approach to problem-solving and experimentation in his scientific work.

### Scientific Contributions
Malus' most notable scientific achievement was his discovery of the polarization of light by reflection in 1808. This discovery led to the formulation of Malus' law, which quantifies the intensity of light transmitted through a polarizer. His work provided a crucial understanding of how light behaves when reflected off surfaces, laying the groundwork for future advancements in optical physics. Malus' contributions were recognized with the Rumford Medal, awarded by the Royal Society for his outstanding work in the field of optics.

### Affiliations and Recognition
Malus was affiliated with prestigious organizations such as the Société Philomathique de Paris and the French Academy of Sciences. His name is inscribed on the Eiffel Tower, a testament to his enduring legacy as one of France's most distinguished scientists. Additionally, an asteroid (11309 Malus) and an island in Antarctica (Malus Island) are named in his honor, further solidifying his place in scientific history.

### Legacy
Étienne-Louis Malus' work continues to influence the field of optics and physics. His discoveries have applications in various technologies, including polarizing filters and optical instruments. His dual career as a military officer and scientist exemplifies the intersection of practical engineering and theoretical research, making him a unique figure in the history of science.

## References

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7. [Source](https://www.toureiffel.paris/fr/le-monument/tour-eiffel-et-sciences)
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