If the laser emits in the visible region then the radiation is perceived as a single colour. The wavelength of light is usually measured in nanometres, or one-thousand-millionth of a metre and is abbreviated to â. â.
A shower or tub equipped with a showerhead shall have a minimum ceiling height of 6 feet 8 inches (2036 mm) above a minimum area 30 inches (762 mm) by 30 inches (762 mm) at the showerhead. The tub/shower is set in an alcove that has as a partial sloped ceiling.
  Standard height for a showerhead is 6'-6 to 6'-8. I prefer the high side of that tolerance. A valve for a shower only is put at about 48, a valve for a tub/shower is â¦ put at about 30, with the tub spout about 6 to 8 below the valve.