What is the wavelength?
The wavelength is very short. The wavelength is less than 10 picometer.
Does it need a medium?
It does not need a medium because it is able to pass through matter.
What is it?
It is an electromagnetic radiation of high frequency. It has high-energy ionizing radiation and small wavelengths compared to any other wave in the electromagnetic spectrum. It has about 10 000 times more energy than other wave in the electromagnetic spectrum. It has no mass or electrical charge. Therefore it is a pure electromagnetic energy. It is emitted by radium-226. It is produced by the hottest region of the universe. It cannot be captured or reflected into mirrors. It travels at the speed of light and is able to move hundreds - thousands meters in the air before its energy is used. As it is able to pass through human tissues, lead (a dense material) is used to slow or stop gamma rays.
What are the uses and dangers?
Gamma-induced molecular changes are used to change the properties of semi-precious stones. For example, white topaz is changed into blue topaz.
In USA, gamma ray detectors are used to scan 30 containers in an hour. This detector is used to scan the containers in ships that are entering USA.
Gamma radiations kills living organisms. This process is known as irradiation. Irradiation is used to sterilize medical equipments, remove decay-causing bacteria from foods and prevent fruits and vegetables from sprouting. This would keep its flavor and freshness.
Although gamma rays can cause cancer, they are used to treat certain types of cancer. This is because the rays will kill the cancer cells too. Multiple concentrated beams of gamma rays are directed on the growth in a procedure known as gamma-knife surgery. By doing this, it would kill the cancerous cells. The beams are aimed in such an angle that it would concentrate on the growth and reduce the chances of damaging the surrounding tissues.
When exposed to 1 sv, it causes blood changes. 2.0 - 3.5 sc would cause nausea, hair loss and hemorrhaging. Anything above 5 sv would increase the chances the death by above 50%. However, when exposed to low doses for a long period of time , it would increase the risk of cancer. For example, nuclear workers is exposed to 19 mSv a year. This increases the risk of cancer by 2%.
Sources:
http://www.epa.gov/radiation/understand/gamma.html
http://en.wikipedia.org/wiki/Gamma_ray
http://science.hq.nasa.gov/kids/imagers/ems/gamma.html
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