Talk:Quantum mechanics/sandbox
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Introduction Glossary · History |
Quantum mechanics ("QM") is the part of physics that tells us how subatomic particles (things that make up atoms) work. QM also tells us how electromagnetic waves like light and radio waves work. Subatomic particles and electromagnetic waves seem to act in very strange ways. QM is a mathematical framework (rules written in math) that helps us understand that strangeness. Quantum mechanics is important to modern physics and chemistry.
Quantum mechanics started when it was discovered that
The higher the frequency, the more energy the electromagnetic waves have, and the more damage they can do. QM showed that electromagnetic waves like light and radio waves are made up of energy packets, called photons. QM later grew to explain the internal structure of atoms. QM also explains the way that a photon can interfere with itself, and many other things never imagined in classical physics.
Some Basic Concepts change
- Quantum, photons, wavelength
Quantum is a Latin word that means how much. So a quantum of energy is a specific amount of energy. Light sources such as candles or lasers shoot out (or "emit") light in units called photons. These units are like packets. The packets each contain a little bit of energy.
Photons are particles, much smaller than atoms. The more photons a lamp shoots off, the brighter the light. Light is a form of energy that behaves like the waves in water or radio waves. The distance between the top of one wave and the top of the next wave is called a 'wavelength.' Each photon carries a certain amount, or 'quantum', of energy depending on its wavelength.
A light's color depends on what its wavelength is. The color violet (the bottom or innermost color of the rainbow) has a wavelength of about 400 nm ("nanometer") which is 0.00004 centimeter or 0.000016 inch. Photons with wavelengths of 10-400 nm are called ultraviolet (or UV) light. Such light cannot be seen by the human eye. On the other end of the spectrum, red light is about 700 nm. Infrared light is about 700 nm to 300,000 nm. Human eyes are not sensitive to infrared light either. Wavelengths are not always so small. Some longer wavelength photons are used for radio signals. The wavelengths for your FM radio can be several meters in length (for example, stations transmitting on 99.5 FM are emitting radio energy with a wavelength of about 3 meters, which is about 10 feet). Each photon has a definite amount of energy related to its wavelength. The shorter the wavelength of a photon, the greater its energy. For example, an ultraviolet photon has more energy than an infrared photon.
Wavelength and frequency (the number of times the wave crests per second) are inversely proportional. This means a longer wavelength will have a lower frequency, and vice versa. If the color of the light is infrared (lower in frequency than red light), each photon can heat up what it hits. So, if a strong infrared lamp (a heat lamp) is pointed at a person, that person will feel warm, or even hot. The surface of the infrared lamp may get hot enough to burn someone who may touch it. However, the person cannot get a sunburn from the photons emitted by the lamp, because those photons do not have enough energy to kill living cells. Humans cannot see infrared light, but we can feel the radiation in the form of heat. For example, a person walking by a brick building that has been heated by the sun will feel heat from the building without having to touch it.
If the color of the light is ultraviolet (higher in frequency than violet light), then each photon has a lot of energy, enough to hurt skin cells and cause a sunburn. In fact, most forms of sunburn are not caused by heat; they are caused by the high energy of the sun's UV rays damaging your skin cells. Even higher frequencies of light (or electromagnetic radiation) can penetrate deeper into the body and cause even more damage. X-rays have so much energy that they can go deep into the human body and kill cells. Humans cannot see or feel ultraviolet light or x-rays. They may only know they have been under such high frequency light when they get a radiation burn. Areas where it is important to kill germs often use ultraviolet lamps to destroy bacteria, fungi, etc. X-rays are sometimes used to kill cancer cells.