Suntan and sunburn are familiar effects of over-exposure of the skin to UV, along with higher risk of skin cancer. Living things on dry land would be severely damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earth's atmosphere.[1] More energetic, shorter-wavelength "extreme" UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground.[2] Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans (specifically, UVB).[3] The UV spectrum thus has effects both beneficial and harmful to human health.

The lower wavelength limit of human vision is conventionally taken as 400 nm, so ultraviolet rays are invisible to humans, although some people can perceive light at slightly shorter wavelengths than this (see below). Insects, birds, and some mammals can see near-UV (i.e. slightly lower wavelengths than humans can see).

As the wavelength of Em spectrum changes Pam the way the different wavelengths interact with smaller matter also changes

As the frequency increases, wavelength gets smaller. Eventually the waves are so small that they can interact with cells, DNA and atoms. This is called Ionizing Radiation

• Am Radio uses low energy and Fm radio uses medium-energy waves

• Tv uses  high-energy waves

• Cell phones use radio waves, stars also  emit-radio waves

• Infrared radiation can also be used to take special photos called thermographs to detect the heat