The apparent depth of an object lying at the bottom of a pool of water (n = 4/3) is, in terms of its real depth h,

1. Refraction at a flat surface: apparent depth = real depth × (n_observer / n_medium). 2. Viewing from air into water: apparent depth = h × (1 / (4/3)) = (3/4) h. 3. The pool looks shallower than it is; (A) inverts the ratio. _Source: syllabus Physics Part II, Ch 9 §9.3 'Real and apparent depth'_