Final answer:
Lasers generally emit light that is coherent and directional, but not all lasers emit light of only one wavelength; some lasers can emit a range of wavelengths. Laser beams cannot be perfectly parallel due to the physical phenomenon of diffraction, which causes light waves to spread out.
Step-by-step explanation:
The property that is not a characteristic of a laser is that 'The light is one wavelength' which implies a monochromatic light source. However, not all lasers emit only one wavelength; some lasers can emit a beam that contains a range of wavelengths or frequencies. The primary properties of laser light include being coherent (all the light waves have the same phase) and typically being quite directional, with all the light traveling in one direction.
Regarding the nature of light as it relates to lasers, even though laser beams are highly directional, they cannot be perfectly parallel due to diffraction, which is the spreading of light waves as they pass through a slit or around an obstacle. This is explained using the finite size of the beam's wavelength and the phenomenon of interference, crucial aspects of wave behavior. With lasers, this spreading can be minimally visible due to the high directionality and coherence of the beam.