CBSE Class 12-science Answered

On account of refraction of light a tank appear shallower than its actual depth. Suppose a ray of light is incident normally and passes straight along OAA'. Another ray of light from O incident at angle get refracted by an angle r deviates away from the normal. In figure OA passes straight along OAA’. Another ray of light from O incident at angle i on XY along OB deviates away from normal. It gets refracted at angle r along BC. When we produce back BC meets OA at I. Hence it’s the virtual image of O. Hence AI is the apparent depth and AO is the real depth.