Definition of critical angle in English:

critical angle

noun

Optics
  • The angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected.

    • ‘For angles exceeding the critical angle, the refracted waves are evanescent and the reflectivity is very close to unity.’
    • ‘Compared with the intensity enhancement for total internal reflection (~ 4 times that of the incident light) at the critical angle, the enhancement for SPR can reach up to 20-30 times higher.’
    • ‘The critical angle c below which x-rays can be efficiently scattered from smooth surfaces is quite small, hence the term grazing incidence.’
    • ‘To minimize fluorescence from the sample and meet the total external reflection condition, the system features a slit that restricts beam divergence in the scattering plane to less than the critical angle for substrate reflectance.’
    • ‘If the beam through m1 is greater than the critical angle, then the refracted beam will be reflected entirely back into m1 (total internal reflection), even though m2 may be transparent!’