Q.Consider following phenomena/applications: P) Mirage, Q) rainbow, R) Optical fibre and S) glittering of a diamond. Total internal reflection is involved in (A) Only R and S (B) Only R (C) Only P, R and S (D) all the four

[!TLDR] TIR genuinely occurs in optical fibres and in a diamond's glitter, but a mirage and a rainbow are both explained without any …

Optical fibre (R) relies explicitly on repeated total internal reflection at the core-cladding boundary -- this is TIR by design. A diamond's glitter/sparkle (S) is likewise due to TIR: diamond's very high refractive index gives it an unusually small critical angle (about 24 degrees), so light entering a cut diamond very often exceeds this critical angle at its internal facets and undergoes multiple total internal reflections before exiting, producing the characteristic brilliance -- a standard, well-known application of TIR even though not derived in detail in this chapter's text. A mirage (P), however, is explicitly stated to involve a continuously and gradually varying refractive index in air (never a sharp interface with a well-defined critical angle exceeded), so true TIR is never possible there -- the relative index between …

Check each phenomenon against the strict definition of TIR (light striking an interface at or beyond a well-defined critical angle) rather than assum …

Assuming mirage and rainbow involve TIR simply because they involve reflection-like bending of light, when t …