physics

Laser fence

Laser fence 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 Laser fence rather than just read about it. In short: A laser fence or laser wall is a mechanism to detect objects passing the line of sight between the laser source and the detector. Stronger lasers can be used to injure entities passing the laser beam.

Key takeaways

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

Reference excerpt

A laser fence or laser wall is a mechanism to detect objects passing the line of sight between the laser source and the detector. Stronger lasers can be used to injure entities passing the laser beam. In fiction, laser fences may have the ability to stop intruders by blocking or injuring them.

Description A laser fence mechanism detects objects passing the line of sight between a laser source and detector. Stronger lasers can be used to injure entities passing the laser beam, as in a mosquito laser. Fictional uses of laser fences often extend the concept so that fences may have the ability to prevent intruders by blocking or injuring them.

Agricultural usage Lasers are used to keep birds from eating blueberries by being perceived as a predator. The European Commission is funding research into a laser fence to scare away rats and other pests.

Border fences The Indian Border Security Force (BSF) has implemented a laser wall system—called LASER Wall—along some parts of its border to stop intrusion.

In fiction

Films In the 1992 film Fortress, prisoners are kept secured by laser walls. In the 1995 film Congo, a laser fence is used as part of other high-tech equipment to defend a camp against vicious gorillas.

Videogames

Laser walls appear frequently in videogames. The concepts of these fictional fences can be compared to other concepts like tractor or repulsor beams and force fields.

Deus Ex: Human Revolution has laser grids which the player can remotely hack with the Remote Hacking augmentation. Monaco: What's Yours Is Mine has a hacker class which use viruses to shut down lasers. Portal 2, with laser barriers as obstacles Sly Cooper: Thieves in Time Titanfall 2 has laser fields to prevent access to areas.

See also Laser Doppler velocimetry Lidar

Notes

Worked examples

Example 1 — a first encounter with Laser fence

Start with the simplest possible case. Write down what Laser fence 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 Laser fence 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 Laser fence 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 Laser fence

In research: Laser fence 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 Laser fence 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: Laser fence is common in secondary-school and first-year university syllabi. It links to neighbouring topics Fences, Fictional energy weapons, Force lasers, so understanding it makes those chapters shorter.
In everyday life: Look for Laser fence 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 Laser fence in 20 minutes

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

Frequently asked questions

What is Laser fence in simple terms?

Why does Laser fence 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 Laser fence?

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 Laser fence.