The angle between the two refracting surface of a prism is called angle of ______.

Explanation

For `T.I.R` at second surface
`r' gt C rArr (A-r) gt C` or `A gt V + C` or `A gt 2C`
(j) On the basic of above examples and similar reasoning, it can be shown that (you should try the following cases (ii) and (iii) yourself.)
(i) If `A gt 2C`, all rays are reflected back from the secound surface.
(ii) If `A le C`, no rays are reflected back from the secound surface i.e., all rays are refracted from second surface.
(iii) If `2C ge A gt C`, no rays are reflected back form the second surface and some rays are refracted from second surface, depending on the angle of incidience.
(k) `delta` si maximum for two values of `i`
`rArr i_(min)` (corresponding to `e = 90^(@)`) and `i = 90^(@)`
(corresponding to `e_(min)`)
For `i_(min) : n_(S) sin i_(min) = n_(0) sin (A-C)`
If `i it i_(min)` then `T.I.R` takes place at second refracting surface `PR`