Why doesn't my laptop emit radiation?

Category: Physics
Published: December 4, 2014

By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and physics professor at West Texas A&M University

Your laptop computer does emit radiation. In fact, your laptop emits several different kinds of radiation:

• 400 to 800 THz electromagnetic radiation. This is the visible light given off by the laptop's screen that makes it possible for you to see what the computer is displaying. Yes, ordinary visible light is a form of radiation.
• 10 to 100 THz electromagnetic radiation. This is the infrared radiation given off by all parts of the laptop due to their temperature, through the everyday process of thermal emission.
• 5 GHz or 2.4 GHz electromagnetic radiation. These are the radio waves given off by the WIFI antenna in the laptop, which are used to connect to a wireless network.
• 2.4 GHz electromagnetic radiation. These are the radio waves given off by the Bluetooth antenna in the laptop, which are used to connect wirelessly to peripheral devices such as a cordless mouse.
• Low frequency electromagnetic radiation. These are the radio waves that leak from the electronic circuitry inside the laptop.
• Nuclear radiation including gamma rays. This is the nuclear radiation emitted through the natural radioactive decay of atomic isotopes in the computer's materials.

Your laptop emits many forms of radiation including waves from across the electromagnetic spectrum. Public Domain Image, source: Christopher S. Baird.

As you see, your laptop emits several different kinds of radiation. But all of the radiation emitted by your laptop is too low-frequency and too low-intensity to be harmful to humans. Also, many of these types of radiation emission are not unique to laptops. Here are some concepts you should be aware of:

1. All objects emit thermal radiation. Simply as a result of being made of atoms and having a temperature, every object constantly emits electromagnetic radiation. For objects that are at human-comfortable temperatures, most of this thermal radiation consists of infrared waves. For hotter temperatures, the thermal radiation can include visible light and even ultraviolet rays. Examples of objects that thermally radiate visible light are stars and incandescent light bulbs. In principle, an object would only cease to emit thermal radiation if it were at a temperature of exactly absolute zero. But a temperature of exactly absolute zero is fundamentally impossible.
2. Most objects contain some amount of naturally-occurring radioactive atoms and therefore emit small amounts of nuclear radiation from the radioactive decay of these unstable isotopes. This nuclear radiation given off by most objects is usually very weak and is part of the background radiation. Even your body contains atoms that are radioactive and are emitting nuclear radiation right this moment. There is a certain amount of radioactive atoms that simply occur naturally, even away from man-made sources of nuclear pollution. Although the amount is small, it is measurable. In humans, the main types of radioactive atoms are unstable isotopes of carbon and potassium. The technique of carbon dating depends crucially on living organisms containing radioactive carbon. In general, background radiation is too weak to harm you.
3. All objects that emit visible light are emitting radiation because light is radiation. This includes candles, fires, light bulbs, televisions and cell phone displays.
4. All electronic circuits leak small amounts of low-frequency radio waves simply by their nature of being an electronic circuit. The very act of an electric current flowing down a curved wire creates a small amount or electromagnetic radiation.
5. All devices that communicate two-way using electromagnetic waves contain an antenna, a laser, or a bulb that emits radio, infrared, or visible radiation. This includes WIFI devices, Bluetooth devices, walkie-talkies, Ham radios, cell phones, television remotes, and remote-controlled toys.

All the forms of radiation mentioned above are typically harmless to humans. So what is harmful to humans? The answer is high-energy radiation. Radiation can either be high energy because each particle is high energy, or the radiation can contain only low-energy particles but enough of them that they add up to a high energy. Examples of high-energy particles include ultraviolet rays, X-rays, gamma rays, and nuclear radiation such as alpha rays, beta rays, neutron radiation, and proton radiation. These forms of high-energy radiation have enough energy per particle to break chemical bonds, and therefore can lead to mutation, cancer and radiation sickness. Even though high-energy particles can be damaging to individual molecules, you still need enough of them to cause significant damage to a human overall. For this reason, the high-energy particles that are present in natural background radiation are overall harmless to humans. Examples of radiation beams that have low energy per particle, but enough particles to be high-energy radiation include bonfires, bright light bulbs, and high-power lasers. These forms of radiation tend to harm humans simply by heating them up to the point of burning them.

Topics: computer, laptop, radiation, radio wave, thermal radiation, wave, waves, wireless