Answer the following questions :
Does the apparent depth of a tank of water change if viewed obliquely ? If so, does the apparent depth increase or decrease ?

Explanation

(a) Real images can be produced by plane and convex mirrors. When the rays that are converging to a point behind a plane or convex mirror are reflected to a point in front of the mirror on the screen, the image formed will be real. This is the case of a virtual object. In case of convex mirror if the converging rays tend to converge at focus or beyond focus then they will not be able to form the real image after reflection.

(b) Virtual image is formed when the reflected or refracted rays are divergent. The divergent rays can be converged on to a point with the help of an appropriate converging lens. The convex lens of the eye serves the same purpose. The virtual image here serves as an object for the lens to produce a real image on the retina. Hence, there is no contradiction.
(c) The rays starting from the head of the fisherman and incident on water become bent towards normal and appear to come from a higher point. So fisherman looks taller.
(d) The apparent depth of tank when viewed obliquely decreases from its value for near- normal viewing. This is due to the phenomenon of refraction of light.
(e) Refractive index of diamond is about 2.42, that is much larger than that of ordinary glass for which refractive index is about 1.5. Using,
`sin i_(c)=(1)/(mu)`
The critical angle for diamond is about `24^(@)`, and that for glass is `42^(@)`. A skilled diamond cutter utilises the large range of angles of incidence in the diamond, from `24^(@)` to `90^(@)`, to ensure that light entering the diamond is totally reflected from many faces before getting out. In this way, light entering the diamond produces a sparkling effect.