physics

John J. Hopfield (spectroscopist)

John J. Hopfield (spectroscopist) is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand John J. Hopfield (spectroscopist) rather than just read about it. In short: John Joseph Hopfield (born Jan Józef Chmielewski; July 8, 1891 – January 8, 1953) was a Polish-American physicist. Hopfield's published research included vacuum ultraviolet spectroscopy and solar ultraviolet spectroscopy.

Key takeaways

John J. Hopfield (spectroscopist) belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect John J. Hopfield (spectroscopist) to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of John J. Hopfield (spectroscopist) from memory before moving on to harder problems.

Reference excerpt

John Joseph Hopfield (born Jan Józef Chmielewski; July 8, 1891 – January 8, 1953) was a Polish-American physicist. Hopfield's published research included vacuum ultraviolet spectroscopy and solar ultraviolet spectroscopy. He was the discoverer of the "Hopfield bands" of oxygen and co-discoverer of the "Lyman–Birge–Hopfield bands" of nitrogen. For about a decade he was an industrial physicist working with technologies for fabricating glass windows, and was the inventor listed on several related patents.

Career Hopfield was born Jan Józef Chmielewski in 1891 in Płock, Poland and was orphaned at an early age. He grew up in an orphanage in Poland and briefly stayed with a Pennsylvania Dutch family in the United States before running away. Despite little formal education, he supported himself by teaching at a district school. Hopfield was admitted to Syracuse University around 1913, completed his A.B. degree in 1917, and then worked as an instructor through 1919. At Syracuse, he had worked as an assistant with Raymond Thayer Birge, who moved to University of California, Berkeley around this time. Hopfield was then admitted to Berkeley with a fellowship, and was awarded his doctorate for spectroscopic work in 1923. He became an instructor and assistant professor of physics at Berkeley, and was awarded a Guggenheim Fellowship in 1928 to work with Friedrich Paschen for a year in Berlin. By the time he left Berlin in 1929, the stock market crash and depression had ended most new faculty hiring. Purdue University appointed him as a National Research Council Fellow for two years. He next was employed in creating the physics exhibit for the 1933 "Century of Progress" World's Fair in Chicago. This was followed by a position with the Libbey-Owens-Ford glass company in Toledo, Ohio. With the onset of the Second World War, physicists were again in great demand, and he moved to Washington, D.C., to participate in war-related research. The end of his career was spent at the Johns Hopkins University Applied Physics Laboratory and at the Naval Research Laboratory in the Optics Division in Washington, D.C. On January 8, 1953, Hopfield died after a brief illness. Hopfield's son, J. J. Hopfield, was born in 1933 and also became a noted physicist, receiving the 2024 Nobel Prize in Physics.

Select publications Ultraviolet Absorption and Emission Spectra of Carbon Monoxide The Ultra-Violet Band Spectrum of Nitrogen New Ultra-Violet Spectrum of Helium Absorption and Emission Spectra in the Region λ 600-1100. New Oxygen Spectra in the Ultraviolet and new Spectra in Nitrogen Preparation of Schumann plates The Ultraviolet Spectrum of the Sun from V-2 Rockets

Patents Line image producer Manufacture of multiple glass sheet glazing units Uniting of glass to glass and metals to glass Multiple glass sheet glazing unit and method of making the same Multiply glass sheet glazing unit Method of fabricating multiple glass sheet glazing units

References

Worked examples

Example 1 — a first encounter with John J. Hopfield (spectroscopist)

Start with the simplest possible case. Write down what John J. Hopfield (spectroscopist) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to John J. Hopfield (spectroscopist) before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about John J. Hopfield (spectroscopist) ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of John J. Hopfield (spectroscopist)

In research: John J. Hopfield (spectroscopist) appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses John J. Hopfield (spectroscopist) in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: John J. Hopfield (spectroscopist) is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1891 births, 1953 deaths, 20th-century American physicists, so understanding it makes those chapters shorter.
In everyday life: Look for John J. Hopfield (spectroscopist) outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study John J. Hopfield (spectroscopist) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what John J. Hopfield (spectroscopist) means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain John J. Hopfield (spectroscopist) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is John J. Hopfield (spectroscopist) in simple terms?

Why does John J. Hopfield (spectroscopist) matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study John J. Hopfield (spectroscopist)?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on John J. Hopfield (spectroscopist).