critical angle

noun

Definition of critical angle 

: the least angle of incidence at which total reflection takes place

Illustration of critical angle

Illustration of critical angle

critical angle: AOB, AO'B', AO''B'' angles of incidence; AOC refracted ray; AO''C'' totally reflected ray; AO'B' critical angle

First Known Use of critical angle

1873, in the meaning defined above

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The first known use of critical angle was in 1873

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