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{{for|other uses|Gamma (disambiguation)}}
'''Gamma rays''' (γ-rays) are [[electromagnetic]] waves with the smallest [[wavelength]]s in the [[electromagnetic spectrum]].<ref>The electromagnetic spectrum is made of many types of waves that are like light, but you can not see all of them.</ref> They were discovered in 1900 by [[Paul Villard]], and named in 1903 by [[Ernest Rutherford]].

Gamma rays are like [[x-rays]], but the waves are smaller in [[wavelength]]. Both gamma rays and x-rays are [[photons]] with very high energies, and gamma have even more energy. They are also a type of [[ionizing radiation]]. Gamma rays can travel through thicker materials than x-rays can.  

Gamma rays are produced by some types of radioactive [[atom]]s.  [[Cobalt]]-60 and [[potassium]]-40 are two [[isotopes]] that emit gamma rays. Cobalt-60 is created in accelerators and is used in hospitals. Potassium-40 occurs naturally. Small amounts of potassium-40  gamma rays come out of their ass  ⏎
⏎
are in all plants and animals. Gamma rays from potassium-40 each have an energy of 1460 thousand [[electron volt]]s (keV). 

Gamma rays and X-rays can also be distinguished by their origin: X-rays are emitted by [[electron]]s outside the [[Nucleus (physics)|nucleus]], while gamma rays are emitted by the nucleus.<ref>Feynman, Richard; Robert Leighton, Matthew Sands 1963. ''The Feynman Lectures on Physics'', vol 1. USA: Addison-Wesley. pp2–5 ISBN 0201021161.</ref> 

== Gamma rays in medicine ==
Gamma rays can also go through the skin to kill cells, such as cancerous cells.
[[Medical doctor|Doctors]] can use [[radiation therapy]] machines which produce gamma rays in [[hospital]]s to treat people with some types of [[cancer]].<ref name=igcse >{{cite book|title=Edexcel IGCSE Physics Revision Guide|publisher=Pearson Education|date=2011|page=38|isbn=9780435046736|first=Steve|last=Woolley}}</ref>

Doctors also use gamma rays to find disease. In hospitals, doctors can give patients radioactive medicine which emits gamma rays. Doctors can find some types of disease by measuring gamma rays which come from a patient afterward. You can also use gamma rays to sterilise (clean) hospital material.<ref name=igcse />

== References ==
{{Reflist}}

[[Category:Nuclear physics]]