ArticleslgStudy

computer science

Haitz's law

Haitz's law is a computer 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 Haitz's law rather than just read about it. In short: Haitz's law is an observation and forecast about the steady improvement, over many years, of light-emitting diodes (LEDs). It claims that every decade, the cost per lumen (unit of useful light emitted) falls by a factor of 10, and the amount of light generated per LED package increases by a factor of 20, for a given wavelength (color) of light.

Haitz's law — main illustration
Haitz's law — illustration

Key takeaways

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

Reference excerpt

Haitz's law is an observation and forecast about the steady improvement, over many years, of light-emitting diodes (LEDs). It claims that every decade, the cost per lumen (unit of useful light emitted) falls by a factor of 10, and the amount of light generated per LED package increases by a factor of 20, for a given wavelength (color) of light. It is considered the LED counterpart to Moore's law, which states that the number of transistors in a given integrated circuit doubles every 18 to 24 months. Both laws rely on the process optimization of the production of semiconductor devices.

History Haitz's law is named after Roland Haitz (1935–2015), a scientist at Agilent Technologies among others. It was first presented to the larger public at Strategies in Light 2000, the first of a series of annual conferences organized by Strategies Unlimited. Besides the forecast of exponential development of cost per lumen and amount of light per package, the publication also forecast that the luminous efficacy of LED-based lighting could reach 200 lm/W (lumen per watt) in 2020, crossing 100 lm/W in 2010. This would be the case if enough industrial and government resources were spent for research on LED-lighting. More than 50% of the electricity consumption for lighting (20% of the totally consumed electrical energy) would be saved reaching 200 lm/W. This prospect and other stepping-stone applications of LEDs (e.g. mobile phone flash and LCD-backlighting) led to a massive investment in LED-research so that the LED efficacy did indeed cross 100 lm/W in 2010. If this trend continues, LEDs will become the most efficient light source by 2020. The theoretical maximum for truncated blackbody white light source (at 5800K colour temperature with wavelengths restricted to the visible band of between 400nm and 700nm) is 251 lm/W. However, some "white" LEDs have achieved efficacies of over 300 lm/W.

Developments In 2010, Cree Inc., developed and marketed the XM-L LED that claimed 1000 lumens at 100 lm/W efficacy and 160 lm/W at 350 mA and 150 lm/W at 700 mA. They also claimed to have broken the 200 lm/W barrier in R&D with a prototype producing 208 lm at 350 mA. In May 2011, Cree announced another prototype with 231 lm/W efficacy at 350 mA. In March 2014, Cree announced another prototype with a record-breaking 303 lm/W efficacy at 350 mA. In 2017, Philips Lighting started offering consumer LED lights with 200 lm/W efficacy in Dubai using LED filament technology, three years before what Haitz's law predicted.

References

External links Haitz, Roland; Kish, Fred; Tsao, Jeff; Nelson, Jeff (1999). "The Case for a National Research Program on Semiconductor Lighting" (PDF). Sandia Report. Optoelectronics Industry Development Association. p. 5. SAND2000-1612.

Illustrations

Haitz's law: Illustration of Haitz's law. Light output per LED package as a function of time. Note the logarithmic scale on the vertical axis.
Illustration of Haitz's law. Light output per LED package as a function of time. Note the logarithmic scale on the vertical axis.

Worked examples

Example 1 — a first encounter with Haitz's law

Start with the simplest possible case. Write down what Haitz's law claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer 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 Haitz's law 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 Haitz's law 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 Haitz's law

In research
Haitz's law appears in computer 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 Haitz's law 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
Haitz's law is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer architecture statements, Light-emitting diodes, Lighting, so understanding it makes those chapters shorter.
In everyday life
Look for Haitz's law 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.
Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Haitz's law” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Haitz's law in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Haitz's law means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Haitz's law out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Haitz's law in simple terms?

Haitz's law is an observation and forecast about the steady improvement, over many years, of light-emitting diodes (LEDs). It claims that every decade, the cost per lumen (unit of useful light emitted) falls by a factor of 10, and the amount of light generated per LED package increases by a factor…

Why does Haitz's law matter?

Because it connects several computer 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 Haitz's law?

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 Haitz's law.

Tags

  • Computer architecture statements
  • Light-emitting diodes
  • Lighting
  • Rules of thumb
  • Semiconductor devices

Keep exploring