However, whereas walking is a low-impact activity because one foot is always in contact with the ground, in jogging and in running, impact is introduced. This is a high-impact exercise that places strain on the body, notably the joints of the knee.
Most background radiation comes from natural sources, while most artificial radiation comes from medical examinations, such as x-ray photographs. Radiation can damage cells and make them cancerous.
Radiation is the emission (sending out) of energy from any source. There are many types of radiation. Ultraviolet (UV) radiation is a form of electromagnetic radiation. The main source of UV radiation (rays) is the sun, although it can also come from man-made sources such as tanning beds and welding torches.Radiation exists across a spectrum from very high-energy (high-frequency) radiation â like x-rays and gamma rays â to very low-energy (low-frequency) radiation â like radio waves.UV rays have more energy than visible light, but not as much as x-rays.adiation exists across a spectrum from very high-energy (high-frequency) radiation â like x-rays and gamma rays â to very low-energy (low-frequency) radiation â like radio waves. UV rays have more energy than visible light, but not as much as x-rays.