science

Hefner lamp

Hefner lamp is a science 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 Hefner lamp rather than just read about it. In short: The Hefner lamp, or in German Hefnerkerze, is a flame lamp used in photometry that burns amyl acetate. The lamp was invented by Friedrich von Hefner-Alteneck in 1884 and he proposed its use as a standard flame for photometric purposes with a luminous intensity unit of the Hefnerkerze (HK).

Key takeaways

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

Reference excerpt

The Hefner lamp, or in German Hefnerkerze, is a flame lamp used in photometry that burns amyl acetate. The lamp was invented by Friedrich von Hefner-Alteneck in 1884 and he proposed its use as a standard flame for photometric purposes with a luminous intensity unit of the Hefnerkerze (HK). The lamp was specified as having a 40 mm flame height and an 8 mm diameter wick. The Hefner lamp provided the German, Austrian, and Scandinavian standard for luminosity during the late nineteenth and early twentieth centuries. The unit of light intensity was defined as that produced by the lamp burning amyl acetate with a 40 mm flame height. The light unit was adopted by the German gas industry in 1890 and known as the Hefnereinheit. In 1897 it was also adopted by the Association of German Electrical Engineers under the name Hefnerkerze (HK). Germany moved to using the new candle (NC) from 1 July 1942 and the candela (cd) from 1948.

1 Hefnerkerze is about 0.920 candelas.

See also Candlepower List of obsolete units of measurement

References

"Lichtstärke und Lichteinheit" (in German). Archived from the original on 2008-04-19.

Illustrations

Worked examples

Example 1 — a first encounter with Hefner lamp

Start with the simplest possible case. Write down what Hefner lamp claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Hefner lamp 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 Hefner lamp 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 Hefner lamp

In research: Hefner lamp appears in science 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 Hefner lamp 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: Hefner lamp is common in secondary-school and first-year university syllabi. It links to neighbouring topics History of science stubs, Lighting, Photometry, so understanding it makes those chapters shorter.
In everyday life: Look for Hefner lamp 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 Hefner lamp in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hefner lamp 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 Hefner lamp out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hefner lamp in simple terms?

Why does Hefner lamp matter?

Because it connects several science 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 Hefner lamp?

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 Hefner lamp.