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 atoms. 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 are in all plants and animals. Gamma rays from potassium-40 each have an energy of 1460 thousand electron volts (keV).
Gamma rays in medicineEdit
Gamma rays can also go through the skin to kill cells, such as cancerous cells. Doctors can use radiation therapy machines which produce gamma rays in hospitals to treat people with some types of cancer.
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. Hospitals can also use gamma rays to sterilise (clean) things as disinfectants do. 
- The electromagnetic spectrum is made of many types of waves that are like light, but you can not see all of them.
- Feynman, Richard; Robert Leighton, Matthew Sands 1963. The Feynman Lectures on Physics, vol 1. USA: Addison-Wesley. pp2–5 ISBN 0201021161.
- Woolley, Steve (2011). Edexcel IGCSE Physics Revision Guide. Pearson Education. p. 38. ISBN 9780435046736.