CBSE Class 10 Science 2020 · Paper 31/3/2 · Question 22

(a) Alcohol is optically denser, because its refractive index ($1.36$) is higher than that of water ($1.33$): a medium with a higher refractive index is optically denser, and light travels more slowly in it. (b) In the ray diagram the ray in water meets the water–alcohol surface obliquely at angle $i$ to the normal and, on entering alcohol, bends towards the normal, making a smaller angle $r$. (c) The angle of incidence is greater than the angle of refraction, $i>r$; by Snell’s law $\frac{\sin i}{\sin r}$ is constant, equal to $\frac{1.36}{1.33}\approx 1.023$.