Dear Gurwinder Kaur,

Acceptance Angle

The maximum angle within which Light will be accepted by an element, such as a Detector or waveguide. In the latter, it is quantified as half the Vertex Angle  of the cone within which Optical Power may be coupled into bound Modes of a fiber. Also called acceptance cone. 

Critical Angle

The least Angle of Incidence at which total internal Reflection takes place. The angle of incidence in a denser medium, at an Interface between the denser and less dense medium, at which theLight is refracted along the interface. When the critical angle is exceeded, the light is totally reflected back into the denser medium. The critical angle varies with the indices of Refraction of the two media with the relationship: sinIc = n´/n where Ic is the critical angle; n´ the Refractive Index of the less dense medium; and n the refractive index of the denser medium.

The formula for critical angle is shown where c is the critical angle, n 1 is the refractive index of the less dense medium, and n 2 is the refractive index of the denser medium.

Hope thishelped you immensely...

All the Very Best & Good Luck to you dear..

Regards,

AskIITians Expert,

Godfrey Classic Prince

IIT-Madras

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