Angle of incidence of a beam of
electromagnetic radiation greater than
\(\pu{70\!^{\circ}}\).
Note:
Ideally the angle of incidence should be greater than \(\pu{80\!^{\circ}}\).
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 748 (https://doi.org/10.1515/pac-2019-0203)