as wover of glass from sortante surfaces bave 1997 (c) A portion of a straight glass rod of diameter d and refractive index n is bent into an arc of a circle of mean radius R, and a parallel beam of light is shone down it, as shown in Figure 15C. (i) Derive an expression in terms of R and d for the no- angle of incidence i of the central ray C on reaching the glass-to-air surface at the circular arc. (ii) Show that the smallest value of R which will allow all the Flight to pass around the arc is given by TIR= Sin 92 opposite of Incidule hoe merim When !! add(n + 1) R R-D 2(n-1) Wind/nLight d Figure 15C R inci

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