Just like other cells, the part of the bacterium that is able to interact with its outside environment is its cell membrane. Generally, the main function of the cell membrane is for barrier and protection. This decides which molecules will be allowed to permeate or not. Hope this helps.
Refraction- bending of light waves (ex. straw in a cup of water looks bent on a side but really is NOT, this is due to refraction, it bends the light waves reflected)
Luminescence- Creation/Emission/Starting or making of light through ways that DO NOT INVOLVE heat.
Ultraviolet- a wavelength that is part of the electromagnetic spectrum its shorter than visible light waves.