Six statements about total internal reflection are given below. (i) A diamond sparkles because its critical angle is small. (ii) In an optical fibre, the cladding is denser than the core. (iii) A fibre guides light by total reflection at its core. (iv) A right-angled isosceles glass prism ($n = 1.50$) turns a ray, entering normally, through $90^\circ$. (v) Light going from air into glass can be totally reflected. (vi) Glass has a smaller critical angle in water than in air. How many of the statements above are correct?