Light Waves Light is an electromagnetic wave. An electromagnetic wave is a transverse wave that is a transfer of electric and magnetic energy. The two fields (electric & magnetic) vibrate at right angles to each other. An electromagnetic wave is made up of vibrating electric and magnetic fields that move through empty space (vacuum) or a medium (matter: solid, liquid, gas) at the speed of light. About 300,000,000 meters per second. The energy that electromagnetic waves transfer is called electromagnetic radiation.

Light and Matter Opaque Translucent Transparent absorbs or reflects all light Absorption When light enters a material but does not leave It is the transfer of light energy to matter Translucent allows some light to pass through Transparent allows light to pass through completely

Reflection Reflection Normal when a wave strikes an object and bounces off incident beam reflected beam

Refraction Refraction Refraction depends on… bending of waves when passing from one medium to another caused by a change in speed Refraction depends on… speed of light in the medium wavelength of the light shorter wavelengths (blue) bend more Longer wavelengths (red) bend less

Visible Light Is all the colors of the EM spectrum we can see. It narrowest part of the EM spectrum Roy G BIV (colors of the spectrum)

Types of EM Radiation Microwaves Radio waves Lowest energy EM radiation FM - frequency modulation AM - amplitude modulation Microwaves penetrate food and vibrate water & fat molecules to produce thermal energy

Types of EM Radiation Ultraviolet Radiation (UV) Infrared Radiation (IR) slightly lower energy than visible light can raise the thermal energy of objects thermogram - image made by detecting IR radiation Ultraviolet Radiation (UV) Beyond Violet Light Ozone layer depletion = UV exposure! slightly higher energy than visible light Types: UVA - tanning, wrinkles UVB - sunburn, cancer UVC - most harmful

Types of EM Radiation X rays Gamma rays higher energy than UV can penetrate soft tissue, but not bones Gamma rays highest energy on the EM spectrum emitted by radioactive atoms used to kill cancerous cells