Editing Circular dichroism (section)

====Extrinsic effects on circular dichroism====
In many practical applications of circular dichroism (CD), as discussed below, the measured CD is not simply an intrinsic property of the molecule, but rather depends on the molecular conformation. In such a case the CD may also be a function of temperature, concentration, and the chemical environment, including solvents. In this case the reported CD value must also specify these other relevant factors in order to be meaningful.

In ordered structures lacking two-fold rotational symmetry, optical activity,<ref>{{cite journal|author=R. Williams|doi=10.1103/PhysRevLett.21.342|title=Optical Rotatory Effect in the Nematic Liquid Phase of p-Azoxyanisole|journal=Physical Review Letters|volume=21|page=342|year=1968|issue=6|bibcode=1968PhRvL..21..342W}}</ref><ref>{{cite journal|author=R. Williams|doi=10.1063/1.1671194|title=Optical-rotary power and linear electro-optic effect in nematic liquid crystals of p-azoxyanisole|journal=Journal of Chemical Physics|volume=50|page=1324|year=1969|issue=3|bibcode=1969JChPh..50.1324W}}</ref> including differential transmission<ref>{{Cite journal| last = Plum| first =E.|author2=Fedotov, V. A. |author3=Zheludev, N. I.  | title =Optical activity in extrinsically chiral metamaterial| journal =Applied Physics Letters| volume =93| page =191911| year =2008| issue =19| doi =10.1063/1.3021082 | arxiv =0807.0523| bibcode =2008ApPhL..93s1911P| s2cid =117891131| url =https://eprints.soton.ac.uk/65831/1/4221.pdf}}</ref> (and reflection<ref>{{Cite journal| last = Plum| first =E.|author2=Fedotov, V. A. |author3=Zheludev, N. I.  | title =Specular optical activity of achiral metasurfaces| journal =Applied Physics Letters| volume =108| page =141905| year =2016| issue =14| doi =10.1063/1.4944775 | bibcode =2016ApPhL.108n1905P| hdl =10220/40854| url =https://eprints.soton.ac.uk/389739/1/specular%2520optical%2520activity%25207rev.pdf}}</ref>) of circularly polarized waves also depends on the propagation direction through the material. In this case, so-called [[chirality (electromagnetism)#Extrinsic 3d chirality|extrinsic 3d chirality]] is associated with the mutual orientation of light beam and structure.