Infrared waves

Thermographic image of a hand that shows t^o of a hand (how much infrared radiation is given .off the surface).

Infrared ("Infra" means "below") waves are just below visible red light in the electromagnetic spectrum. They're given off by all hot objects, and you can feel them as warmth on your skin. Infrared waves have wavelength between 750 nm and 1 mm and frequencies from 405 THz to 300 GHz.

Infrared waves are used for many things such as:

• T hermography

• Night vision

  

• Tracking

  

  Infrared port

• Communications

  

• Heating

• Meteorology

• Astronomy

The most common uses of IR waves are remote controls and infrared motion alarms. IM Alarms are made using passive infrared sensor which is an electronic sensor that measures infrared light radiating from objects in its field of view.

Dangers

The danger to people from too much infrared radiation is very simple - overheating.

Light

Beam of light being dispersed by a prism.

Our eyes can detect only a tiny part of the electromagnetic spectrum, called visible light. Light waves are given off by anything that's hot enough to glow. EMR in the visible light region consists of photons, which have properties of both waves and particles. White light is actually made up of a whole range of colors, mixed together. We can see this if we pass white light through a glass prism. Light has wavelength between 390 nm and 750 nm and frequencies from 770 THz to 400 THz.

W e use light to see things! As the Sun sends so much light towards our planet, we've evolved to make use of those particular wavelengths in order to sense our environment. Light waves can also be made using a laser. This works differently to a light bulb, and produces "coherent" light. Lasers are used in Compact Disc & DVD players, where the light is reflected from the tiny pits in the disc, and the pattern is detected and translated into sound or data. Lasers are also used in laser printers, and in aircraft weapon aiming systems.

Dangers

Too much light can damage the retina in your eye. This can happen when you look at something very bright, such as the Sun. Although the damage can heal, if it's too bad it'll be permanent.

Ultraviolet waves

UV waves are called like that because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet. These frequencies are invisible to humans, but visible to a number of insects and birds.

“Black light” lamps

UV is given off by the Sun in large quantities and lamps that are called “Black light” lamps. There are also some other UV lamps and LED’s and lasers. Ultraviolet waves have wavelength from 10 nm to 400 nm and frequency from 30 PHz to 750 THz.

UV has a has a wide range of applications. People use UV for:

• Getting a sun tan

• Detecting forged banknotes

• Killing microbes

  

  luminescent characteristics on banknotes

• Sterilization of products

• Revealing of invisible ink

You can also mention that your clothes sometimes starting to glow in black light. That’s happening because substances in washing powder "fluoresce" when UV light strikes them - they absorb the UV and then re-radiate the energy at a longer wavelength.

Clothes glowing under backlight

Suitable doses of Ultraviolet rays cause the body to produce vitamin D, and this is used by doctors to treat vitamin D deficiency and some skin disorders.

Dangers

Large doses of UV can damage the retina in your eyes, so it's important to check that your sunglasses will block UV light. Large doses of UV cause sunburn and even skin cancer.

X-Rays

An example of radiograph

X-rays were discovered by Wilhelm Röntgen in 1895. X-rays are very high frequency waves, and carry a lot of energy. That’s why they can pass through most substances. X-rays have wavelength from 0.01 nm to 10 nm and frequency from 30 EHz to 30 PHz. X-rays are given off by stars, and strongly by some types of nebulae. X-rays can also be generated by an X-ray tube.

Because of x-rays’ ability to pass through surfaces, they widely used in medicine to see inside people. The pictures got using x-rays are called “radiographs”.

X-Ray Machine

X -rays are also used in airport security checks, to see inside your luggage. They are also used by astronomers - many objects in the universe emit X-rays, which we can detect using suitable radio telescopes.

Dangers

X-ray scanner in airports

X-Rays can cause cell damage and cancers. This is why Radiographers in hospitals stand behind a shield when they X-ray their patients. Although the dose is not enough to put the patient at risk, they take many images each day and could quickly build up a dangerous dose themselves.

G amma Rays

Emission of a gamma ray from an atomic nucleus

They are extremely high frequency waves, and carry a large amount of energy. Gamma rays are given off by stars, and by some radioactive substances. They pass through most materials, and are quite difficult to stop - you need lead or concrete in order to block them out. Gamma rays are biologically hazardous. Their wavelength is less than 0.02 nm and frequency is more than 15 EHz.

Because Gamma rays can kill living cells, they are used to kill cancer cells without having to resort to difficult surgery. This is called "Radiotherapy". Gamma rays are used for killing microbes and sterilization of food this is known as "irradiated" food, so that it will keep fresh for longer. Gamma rays are also used to sterilize medical equipment. Moreover gamma rays are used in astronomy.

The Moon as seen by the Compton Gamma Ray Observatory

Dangers

Gamma rays cause cell damage and can cause a variety of cancers. They cause mutations in growing tissues, so unborn babies are especially vulnerable.

Bibliography

Used sources:

http://en.wikipedia.org/wiki/Electromagnetic_radiation

http://en.wikipedia.org/wiki/Radio_waves

http://en.wikipedia.org/wiki/Microwave

http://en.wikipedia.org/wiki/Infrared_radiation

http://en.wikipedia.org/wiki/Visible_spectrum

http://en.wikipedia.org/wiki/Ultraviolet_radiation

http://en.wikipedia.org/wiki/X-ray

http://en.wikipedia.org/wiki/Gamma_ray

http://www.darvill.clara.net/emag/

http://en.wikipedia.org/wiki/Electromagnetic_spectrum

http://www.wisegeek.org/what-is-electromagnetic-radiation.htm